My daughter brought home a lab puppy which had been left chained outside an abandoned home without food and water. The puppy's been here a little less than two weeks. It's probably around 3 months old. It had been eating fine until last night, when it really didn't eat that much. Kind of picked at its food. Seemed to be drinking fine. Also was playing with the grown labs, but not as much as previous days. It didn't eat anything tonight. Not playing as much, either. We did give him a shot today (may have been its first, I have no way of knowing. And wormed him as well). Any ideas? I'm thinking that if the puppy doesn't start eating by tomorrow, it's time to go to the vet.

Don't fool around and let this go into the weekend when you pay through the nose for any vet you can find. Trust me, not normal behavior. Could be a reaction to the shot and worm medicine, but it should have gotten over that.