Red bump inside lip? Please help me!?!?!? Is this serious?!?!?

I have a red bump inside my lip. It's like, there is a ball inside of it, and if i were to squeeze it, stuff would come out (sorry for being gross) It's not razor burn. It doesn't itch or anything, but it hurts to put pressure on it. It's about the size of a pebble. And I am 100% it's not an STD i'm a 15 year old virgin. Could it be a cyst? Will it go away? I do not want to tell anyone about it unless it is serious. What do you think? I am worried! I have never had this before.