I have a lump on my thumb joint and swelling. Using my hand causes shooting pain in the thumb. Xray normal. Test to determine cause? Type of dr?

Hand surgeon. Plastic or ortho. Probably need only exam then surgry.
Likely trigger thumb. If the lump is on the palmar side of your thumb by the web space it is likely "stenosing tenosynovitis" or "trigger thumb" this can cause clicking or locking. It may respond to a steroid injection. If not siimple release under local anesthesia is immediately corrective.