I have many bumps inside my cheek skin? Can I only feel them in my mouth not outside.

Can be normal. Without seeing them it is hard to give you a diagnosis. Often these kind of appearances are normal. See your Dentist for a clinical examination and diagnosis and any treatment options you might need . Good Luck.
Bumps. Unfortunately "bumps" is not a medical/dental term. You will have to be examined (see your Dentist) to determine what exactly it is that you are talking about. Probably nothing to worry about, but see your Dentist to make sure.