might be recurrent carpal bone subluxation, wrist sprains can leave the ligaments lax causing excessive movement of the carpal bones, if it is it can be difficult to fully amend, try a physio...it may need resetting, strapping or splinting...combined with wrist exercises...

had a gentleman like that who kept complaining of wrist pain...on examination a lump ontop of the wrist that was moveable...

if the pain is unbearable...you may need to meet up with ur gp for pain control...

let us know how u get on