unidentified mouth blister

I seem to have developped a blister of some sort in my mouth. It does not hurt but has been there for 3 weeks now. It is a small sphere below the surface of the skin. It is very hard I have tried to pop it but have had no luck. It is cumbersome as it is very close to my lips and teeth and so I bite it often. What can it be and what should I do?

[Jenn1288]

A couple of years ago I had the same thing. Mine started out as being a blister that didn't hurt located on the same spot as yours, after over a month though it turned purple-greenish and I had to have it surgically removed. They sent it to the lab, said it wasn't harmful but never told me what it was. But you should definitely see an oral surgeon. Good luck!