What Causes Blister Near The Tonsils?

Hey! I had my tonsils taken out in July of 2009. I don't know how relevant that is, but i thought I would go ahead and put that out there. I now have a small pimple looking thing next to my right tonsil. It doesn't hurt. I don't have a fever. I have no clue what it is. It has been there for about 2 weeks now. I just want to know what it may be and how worried I should be.