Hard to say really.If there was no tell tale sign of a cut or bleeding.He may have landed on it the wrong when when he leaped into the brush.Could be a slight sprain or even twisted it the wrong way.Either can be painful enough for the dog to not want to put any pressure on the leg.I'd also look for swelling.A twist or sprain can last for a few days so keep a eye on it..if you see absoultely NO improvement in 3-5 days or you think its gotten worse,then by all means it time to see the Vet.Good Luck Take care Jackson..