If he is putting weight on it and letting you move the injured limb back and forwards then it is unlikely to be a break. Make sure he rests, no jumping about!
As to the vet, when Adam sprained his leg (playing with a lab and a lurcher down the park
) I didnt take him straight away. He only went after he persisted in chasing the cats and kept respraining his leg! Luckily my vet is lovely and didnt charge me for doing pretty much the same thing that I had done to his leg to check it!!LOL