My son went through the same thing at this age. We ended up at PT for a whole summer, and that helped tremendously. Before going to PT we took him to a sports doctor and he had X-rays done just to check his growth plates. (thankfully those were fine) The doctor also checked his hips and determined that one side was higher than the other thus making one leg appear longer, which he over compensated for while he was running and was putting a lot of stain on the Hamsting. In PT they worked on getting his hips back to normal and strengthening the muscles around it.
We're very thankful for the sports trainers at Man City Cup the weekend it started bothering him. They are the ones that suggested that we see the right people. Otherwise, we probably would have just waited it out and done the wrong stretching exercises.
