Popping Out Cartilage In Rib Cage High Up On The Left Side Of His Chest After Hurting Back. How Long To Heal ?

Hi , My son has popping out cartilage in his rib cage high up on the left side of his chest . He hurt it back in September of last year. At first he kept doing his normal activities...he is an avid tennis player, hiker and golfer, and goes to the gym on a weekly basis. He is 24 years old. He didn t go to the doctor until about December. They just gave him anti-inflammatories and cream to rub on it which didn t really help much.. They did not diagnose him with anything in particular at that time. He also has a knee injury that he has been going to a chiropractor for. He decided at the beginning of January to mention the pain in his chest and his chiropractor examined him and popped the cartilage back in. This, he told my son, was the cause of the pain he had been experiencing. Since then he has been going back to the chiropractor at least once or twice a week to pop it back into place. He has not done any kind of activities since the end of December now. There does not seem to be any change in his condition though. Can you tell me how long it could be before it heals? Will he be able to go back to the sport activities that he loves?