It might be a mucocele which is a blocked mucous duct, or a lipoma,or a fibroma, all of which are harmless but you should see an oral surgeon for a definitive diagnosis.
My 10 year old son has a pea shaped growth on his gums. It looks like a blister , it is full of blood. Is this somthing that I would see a dentist for or his regular doctor? What could it be? It has been there for about a month he told me today. I can not find a picture of it anywhere on line.