I have a "pimple" on the roof of my mouth. Is this normal?

[madhira]

I appear to have noticed a pimple on the roof of my mouth. I don't know what caused this as I have not done anything extraordinary that compromises my health. It looks like one of those pimples with water inside them. It's small and it doesn't hurt or anything, just bothersome. Is this common/normal?

I've read that they are trapped saliva or something and are usually harmless. I could be wrong though.