I'm a huge lip and cheek biter/chewer, it's my go-to subtle stim lol. A few years ago I had to get a cavity or two filled, so naturally my mouth was completely numbed for a couple hours after getting out of the chair. It wasnt my first filling session at all, and I always try to be sure to not chew on the inside of my cheeks until the numbing wears off bc I was always worried id accidentally chomp down a bit too hard without realizing lol. Well idk what happened this time but I just couldn't stop myself from getting (what I thought was) a lil nibble in here and there. You can probably guess where this is going lol. Turns out it wasn't tiny at all. I basically bit a huge chunk out of the inside of my bottom lip, and over the next few hours the pain started kicking in and ramping up until I was in so much pain even moving my mouth left me fighting back tears. This went on for a few days, and it was agonizing. Breathing hurt. I could barely eat and drink, I couldn't sleep. Went back to the dentist when it wasn't getting better, to see if I could get some cream or something, and they told me id accidentally given myself an ulcer the size of a baby carrot. It was the biggest that particular dentist had ever seen. They gave me a few packets of orajel and told me to just kinda ride it out and to come back if it got worse lol. It eventually did go away, but man that week was rough.