Ross, come on... Look at the circumstantial evidence:

Hitting full force with bare knuckles would break your hands if you can throw a half decent punch. Bone is harder than concrete.

One thing I will concede is that being hit once with bare knuckles will damage your skin more than with gloves.

a) Haye's hand was fine.
b) Chisora didn't have a scratch on him, no cut, no substantial swelling or bruising, nothing.

It clearly wasn't a concussive punch or Haye's hand would have shattered and Del Boy would be leaking.
YOU CAN'T PUNCH AS HARD WITH BARE KNUCKLES...