We went through this last year. My son had the exact same diagnosis. We used an ASMI recommended ortho who told us the only way to heal this is through rest. The doctor also gave him a series of band exercises to keep his shoulder healthy. They prescribed 3 weeks of rest to start. That didn't help so he had to rest another 3 weeks. About a month into throwing he had a setback that caused him to rest another 3 weeks, but since then he has been fine. There is very little information available on these types of injuries so it was very frustrating when we went through it. Best of luck to your son.