I'm SO glad he made it through the surgery OK. Bruising and swelling are worst the second day after surgery, so if he gets a bit more puffy today and tomorrow, that would be expected. I would be more concerned with pain control the next couple of days as opposed to infection, although I supposed the longer the surgery, the higher the risk of infection.
One word of caution if your vet used a mattress suture, ie one long, continuous suture: My rats always chew out a few stitches, but because the others are there, things don't open up. The concern with one continuous suture is that if they chew any part of that suture, the whole thing will come open, instead of one little spot. Just FYI...
Kisses to the man, and to his brother too so he doesn't feel left out!