The way the store made it sound, the bumps showed up gradually over the past few weeks, which is why I'm a bit hesitant to think they're bite wounds.

They didn't know what was wrong with him, and didn't want to pay to take him to a vet. They were hoping someone would feel sorry for him and take him home/fix him up. I need to go back later this week anyway, so I'm hoping to talk to the girl who actually cares/feeds the snake in order to get more details. She's the one who supervises when they feed, so I'm guessing she'd notice if he'd gotten bit. (of course, I'm sure the vet can tell me either way what they are, I'll just breathe a lot easier when I know what it is. )