Leave or treat Severs Disease ?

My 13 yr old son has pain at the back of his left heel. It was diagnosed by his family doctor as severs disease and we were told that he would just grow out of it. He is having trouble with sport and its making him miserable. I searched on the web and lots of treatments are mentioned, so I not sure if we should do something or just leave it as was suggested. Does anyone have some insights that could help?