My book has a few place names that are also present in other pieces of media, for example, one of my cities is called "Manalin" and I just found out that there is a planet in Star Wars also called Manalin. The capital of one of the kingdoms in my book is called Pokrovka, but I've also recently discovered a video game series where another city is also called Pokrovka. I took the name from a commune in Ukraine. Will these be a problem?
You can't copyright individual words, such a city names. You could trademark them, but unless it is a major central location, no one will do that.
Leaving legalities for practicalities, what you want is to avoid confusion.
If a coined name is distinctive and at least somewhat prominent, you might want to vary it. A planet mentioned once in a single line of dialog in Star Wars, where no action takes place or is even reported, will not matter. But I wouldn't call a planet "Alderaan" (the planet destroyed by Vader) or use the name of Luke's home planet, unless you are inviting readers to assume that they are the same.
"Centerville" was the home town of the VP character in Have Spacesuit, Will Travel but it is so generic that anyone should feel free to reuse it.
A name used in an obscure work that few have read should also be fair game.
In short ask yourself, "how likely is it that some significant number of readers will be confused, or make an association I don't want them to?"
Legally you ought to be in the clear, especially in places with real-world parallels. I set my comic in Santa Mira, a fictional California city, precisely because it's been used in so many fictional works ... although I've also made no effort to reference any of them in the comic.
Legally, you're probably ok. Trademark would become an issue if it seemed like you were trying to profit from an unauthorised association with Star Wars. As it is now, it doesn't sound like you've crossed the line.
But it's so easy to change them, you might as well play safe and make them uniquely yours. For example: Manalinsk and Pokroviya. Or Malalina and Pokrograd. A quick google will show you whether a name has been used before..