I'm a new dog owner, and I have a 1 year old male rottie/lab mix about 60 pounds.
He was running around the yard and now he's limping on his right rear leg. I don't see anything, there's no temperature and he has no swelling. Yet when he walks he lifts the leg up in the air as soon as stops. He does have a dewclaw, and seems to be licking that. Do I need to take him to the vet or can I wait overnight? Any suggestions?

I think it will be safe to wait overnight. If he is still favoring it tomorrow - I give your vet a call. Please do not give your dog any pain medications without the advice of a vet.