I have white bump on my inner lips. What is it and will it go away by itself?

Mucous cyst. This can represent cyst from gland in lip. It may be result of trauma from tooth. It will not go away but it can temporarily shrink with the use of a wet tea bag on the inner lip.This ma require mior surgical procedure.
Oral lesion. There are many possibilities: leukoplakia, a papilloma, a small fibroma, even a tumor. I would see your dentist or an ent.