I have a blister-like growth on my thumb. Thought it was part of the arthritic decline in my hands, (I m 73!) but it seems to be something else. it s only painful when pressed firmly. The blister-like part, which is an inch wide and an inch and a half long, seems to emanate from a tiny, slightly darker bump at the top. Noticed it about two months ago and have been just hoping it would resolve on it s own as it seems to be causing no problems other than cosmetic. Any thoughts on what this might be? If I need to see a doc, should it be my internist or my dermatologist?