How does one stop biting the inside of one's lip or cheek?

Positive or negative reinforcement might help. I scrape my head and I stopped for a bit after I told my gp. Being accountable and keeping records helps. I would document all times that you bite yourself, that way you have a way to quantify it.

I play with my beard and have a fidget spinner when I am in public. I rarely self harm in public.

I read a book on my similar condition and it said to find others like your self and talk about it.

I’ve had that happen and just like you, if it happens once, it will happen the next day or soon after. I find it may happen if I’m eating something where I’m really chomping down, like a bagel or steak. What helps is if I am really conscientious about chewing and also trying to chew on the opposite side of my mouth. It hurts like hell when I bite the inside of my cheek and sometimes if I put a napkin in there, I will see a tiny drop of blood.

The only reliable way to stop yourself from biting your lip/tongue/inside of your mouth, is to remove all your teeth.

It happens when I eat too fast.

Have to be careful for several days and then the inflamed area should go back to normal.

Eat slower, smaller bites to prevent it, when it does happen, swirl some crushed ice in your mouth and stop eating for a few minutes. Don’t try to multitask while you are eating. Look up some facial exercises online to do daily to strengthen and tone your cheeks.

It’s possible it was inflamed from a virus and that’s why you bit it in the first place. That usually passes in less than a week. You can try some ice chips or take antihistamine if it is really bothering you, but my guess is it only bothers you a lot when you bite it.

Some people bite their cheek a lot because their teeth aren’t aligned well, but I don’t think you are talking about that from what you wrote

I puff out my cheeks like a chipmunk for a few seconds every so often. That pushes my cheeks out a little and maybe applies pressure to the newly formed bump.
It seems to work for me even though the physics doesn’t seem quite right.

Yes. About the same as you describe. I start getting frustrated and concerned about it the more I do it, and that eventually helps me pay enough attention to stop doing it. Last time, it took me about 24–48 hours (and a half-dozen painful bites) to stop.

I think once or twice, I’ve tried putting something in my mouth between the teeth and cheek, and that helped, but was also annoying.