(yes I'm aware that this was asked over a year ago, but I always like to put my two-cents in when it comes to writing advice)
My advice might have been said already, but I tend to write a lot of torture scenes ranging from stab/gunshot wounds to being eaten alive by vultures (fun times, I know), and from what I've learned as I've written and watched people's comments on my work, less is more. Of course, there are always exceptions, because let's face it, most rules of writing can be broken at some point or another. I'm not entirely sure how much you're going for, so I'll start small and build up. That way, if something I describe starts getting uncomfortable, you know not to keep reading.
Lots of people before me have suggested flashing through the actual torture bit, but if you actually want to write it out, but are still scared, try this: psychological torture. Be warned, though. This kind of torture typically takes a long time if there's no physical pain involved. Like, months. I've read too many books both published and otherwise where psychological damage without pain is gained within the first few minutes of torture. That's not realistic. There's different ways to do this, but just Google "psychological torture" and you'll find some fun stuff. Remember, torture is not about the pain itself. It's about the fear of pain. Use this. It's your most important tool. Get good at describing fear, and you'll have your torture scenes, as well as your suspense scenes, come together coherently a lot faster.
Say you want to include pain. Sounds good. One thing to know, though, is that if the pain is intense and long enough, the victim will say anything to get it to stop, whether that's true or not. If your torturer is experienced, they'll know this. Be aware of humans' reactions to pain. Again, Google is your friend. You can even find a lot of this without running into really graphic stuff.
My number one piece of advice? Take it slow. Write short, quick sentences describing initial shock and pain, and then use longer sentences to describe emotions and thoughts. If you want to add more description and more pain, spread it out among the other parts. People in intense pain tend to feel things almost slower. Take advantage of that passage of time and take breaks from the actual pain and wounds to focus briefly on things like tears, restraints, sounds, glimpses of the torturer's face, etc. Spread the wounds out in your writing. This gives the effect of slowing time to the reader as well, and even if you aren't graphically describing the actual torture, they might feel right there next to the narrator, helpless and afraid.
All this other stuff is just for if you want more advice :)
Most successful writers who include pain (who aren't writing for the horror genre, because that typically focuses on gore) also include the shock. For example, when a character gets stabbed, it may take them a second to realize what had happened, especially if it came as a complete surprise. If this character is the narrator, first or third, this second can feel a lot longer, and you can do some pretty powerful things with that brief moment of silence. Therefore, you have part of your scene written without describing gore or even pain.
Next comes the actual, physical pain. If you want to keep it light, keep it brief. Quick visualizing words for pain include stabbing, burning, searing, shocking, etc., though I find myself using those a bit too frequently, so you can always come up with more creative words (or just use a variety). This is your focus. After all, you want your readers to feel (or at least imagine) what your character is feeling. If the narrator is the victim, you can do a lot with this. Look up specific reactions to pain, because other than the pain itself, your character can also sweat, clench their muscles/teeth, scrunch their face up, have trouble breathing/moving, etc. If the narrator is watching, a good idea is to briefly include what the victim looks like they're feeling, and the narrator's reaction. For example, the narrator might vomit at the sight of the victim being stabbed.
If there's a wound involved (which there almost always is), an option is to briefly describe it physically from the narrator's point of view. If they can't see it, skip the physical description, or add how they think it looks. This can be as brief as "blood oozed from the knife wound" or you can go into more depth, though I'd keep it to three sentences, maximum, because as mentioned in other responses, you don't want to numb your reader. This is not your focus. This is just to give your readers a quick visual. Personally, I'd rather read about the pain and what the character is going through rather than what it looks like.
The trick with this: constantly (you know, to an extent) remind the reader that they are injured, hours, days, and sometimes weeks after the fact. If you don't, it's unrealistic. If you Google modern torture cases, you'll get a pretty good idea of how much psychological damage torture does. You have to keep this up through the rest of the story. This is one rule you should never break.
Other quick tips: 1. giving the torturer a good, rounded reason to actually torture makes the scene really creepy without much pain. You can slowly drop hints of their motivation, and let the readers figure it out, or you can have them actually mention it. I would suggest the first, but to each his own. I've seen it both ways. 2. remember that your character most likely can't get up and walk away afterward, even during a breakout with others helping them (unless they're carried uselessly). Don't pull a Mandalorian and go "stop. I can stand" and have your character walk off as if they didn't just have severe brain injuries (no hate on the show, though, I love everything about it except that one scene).
Really, just do your research and incorporate it in your writing, and you'll most likely do just fine.
As mentioned in the beginning, I tend to write pretty violent and graphic torture scenes compared to the example above, but the basics are the same. Hope this helps!