OP I think your profile is private so can't see the pic, but I'd agree with Heebie that if it's working ok and not too sore, it's probably ok. If that changes over the next day or two get him checked over.
The mind boggles at quite how he managed that one though!
Red flags - severe pain, swelling that persists/comes back/gets worse, numbness or pins&needles in his hand (particularly in the thumb and first 2 fingers on the palm side), inability to clench his fist, inability to move his thumb across his palm to touch his little finger (moving little finger only doesn't count, has to be the thumb that moves).
If he has none of those then he doesn't need to worry (except about the ability to shut his wrist in a door!) - any of the above signs and he might have ongoing bleeding or pressure on his median nerve.
Patients on warfarin always bruise spectacularly and it spreads up between the skin layers so the bruises look huge!