What you have there is something called a habit.

What you need to do is break the habit by doing something else.

Perhaps sucking a sweet every time you find yourself biting the inside of your check or you could just have a wank which would be much more fun.

mm thanks` ive tried the sweet thing but it didnt always work.

Well, to chew the insides of your mouth, you need to have your teeth available. Obvious yes but, find something to occupy your teeth like a piece of clean hard wood or hard rubber etc. Much the same as a smoker giving up smoking, you need to replace one bad habit with one that is more acceptable. I wish you good luck.

get a dentist to yank all your teeth off

OCD?

i used to grind my teeth when i was a kid.and now i have this weird thing where i lick my fingernails,i dunno why i do that.

Try chewing gum instead

well if it hurts u and makes u bleed dont do it...suck on suckers or gum w.e works