Question

I have 7 month old German Shepherd puppy. He is happy, eats well. He has been limping one of his front legs for about couple of weeks. This limping happens when he has been running in a dog park for a little while, it doesn't seem to bother him but bothers me because I see him limping. When I feel his legs and paws and check him out he doesn't flinch or pull away so there seems to be no pain related to it. A month ago when he got neutered I noticed a bony mass kind of thing little above his right shoulder, it's not sore or anything. I mentioned this at the vet and I was told that it feels like a bone and that GSD's are prone to have "pano" and that he would grow out of it. With his neuter he got a full check up and clean bill of health stating he is in excellent condition. I still can feel the bony mass, though it's gotten smaller. Should I be worried about his limping or just let him grow and play? He is 7 MO and weighs 78 lbs.