What could this rough patch on the inside of my cheek be from?

The left side of my cheek is kind of rough, and I didn’t burn it, and to the best of my knowledge, didn’t bite it either. I didn’t notice it until yesterday, but it’s really annoying, and if at all possible, I’d like to make it go away.

Except I have no idea how it got there.

Ideas?

I know this is a stupid, stupid question. But it’s really, REALLY annoying!