I simply let my character survive a wound that he shouldn't have survived, and then left a note at the bottom about what would have really happened.

As a reader, this would break my immersion and ruin the story, everything after that is BS, I know it, the author knows it, and did it anyway.

Change the plot point.

Change the injury to something crippling (for the moment) but survivable.

Make it so the injury isn't what the character thought it was.

Make the character recognize the gravity of the injury and do something about it, to make it non-fatal.

Invent another character to prevent the hero from dying, even if you have to write 10,000 words.

Or, as a last resort, just don't tell us. This is fiction, an entertainment, so take the liberty without apologizing for it. If 10% of readers call BS on it, you still entertained 90% of them. Stop worrying about "justification" or your "integrity" or "honesty".

Yes, I'd like my fiction to be plausible; and I would probably choose to rewrite, but I don't expect deep plausibility in fiction that will withstand any level of research. IRL I am a scientist, but I do not expecting readers to take my fiction as literal truth or withstand close scrutiny. You just need some surface plausibility, or as we call it in science, "hand-waving" justifications a reader can accept without much thought, and read on.

Don't let your ego get in the way of writing an entertaining story.

I simply let my character survive a wound that he shouldn't have survived, and then left a note at the bottom about what would have really happened.

As a reader, this would break my immersion and ruin the story, everything after that is BS, I know it, the author knows it, and did it anyway.

Change the plot point.

Change the injury to something crippling (for the moment) but survivable.

Make it so the injury isn't what the character thought it was.

Make the character recognize the gravity of the injury and do something about it, to make it non-fatal.

Invent another character to prevent the hero from dying, even if you have to write 10,000 words.

Or, as a last resort, just don't tell us. This is fiction, an entertainment, so take the liberty without apologizing for it. If 10% of readers call BS on it, you still entertained 90% of them. Stop worrying about "justification" or your "integrity" or "honesty".

Yes, I'd like my fiction to be plausible; and I would probably choose to rewrite, but I don't expect deep plausibility in fiction that will withstand any level of research. IRL I am a scientist, but I do not expect readers to take my fiction as literal truth, I don't expect my fiction to withstand close scientific scrutiny. You just need some surface plausibility, or as we call it in science, "hand-waving" justifications a reader can accept without much thought, and read on.

Don't let your ego get in the way of writing an entertaining story.