I am currently in school to become a Registered Vet Tech. In my clinicals, I have seen many neuterings! The way they remove the testicles would definately cause swelling and bruising. I have been lucky to be back at the same clinic when the owners brought there pet in for post op check and yes, this is normal. It can be very disconcerting to see the bruising and swelling and all animals lick their wounds, sometimes to the extent of more damage. Unless this vet clinic is a shoddy one, the vet is not going to lie to you about your pet or his condition.