I would say if the vet says he's doing well, you have to go with that, but if you have any doubts, a second opinion never hurt anything. It could be that he was traumitized, or the meds like the others mentioned, but it could be that he's in pain too. Have you discussed this behavior with your vet and he still said Jock is doing good? If not, that would be a first step.

Good luck and please let us know what you find out.