Pain coming from a hard lump on palm below the ring finger, what might this be?

My Husband is a drummer for a rock band and last night he experienced great pain from his palm up his arm, it was a bit swollen and we found a quarter size hard lump in the palm of his hand about an inch below his ring finger.  He is also a diabetic.  We do not have very good medical insurance and are looking for possibilities for what this may be or what we can do to relieve the pain.