For about a month, I have had a small (size of a pea) growth on the palm side of the ring finger of my left hand, between the second and third joints. I had experienced a sharp pain when I grabbed the handrail of my treadmill machine. At first I thought I would have a bruise on the finger, but after a day or so, this lump appeared. It is painless, except for an occasional stinging sensation. I can move all the joints in the finger. I have previously been diagnosed with marginal zone lymphoma and am concerned that this lump could be a tumor.