Just A No-Good Cheekbiter

Okay, maybe I'm just retarded...but are you ever eating something - maybe a fried peanut butter and pork hock sandwich on rye, ya know...just for example - and all of a sudden you bite down really fucking hard on the inside of your cheek?

It hurts like hell so much you go look in the mirror to see if you drew blood.

Then, after a thorough examination, you go back to eating said sandwich and you do the exact same thing again. You bite the same spot, but even harder and this time you do draw blood.

What the hell is that all about?