Bumps etc. in mouth...?

I have a question about these bumps in my mouth. They look and feel exactly like pimples on the skin, and they are completely painless. I don't know they are there until I feel them with my tongue. They only appear when I am stressed, which I have been very stressed lately, and then after a couple of days they go away. Everything I have read says they are harmless, and they are probably just a mild form of canker sores, and it is common to have something like that during a time of mental stress. However, I have this one bubble-like thing on the inside of my cheek that has been there for a few months now; it feels like those blisters you get on your heel when a shoe rubs the skin for too long. It is very small, but it won't go away. I am 16. Should I be concerned?