The first injury is not even mine! My 13 year old boy has developed Severs Disease, so I spent a lot of time looking for resources on that. Severs disease is like a stress fracture of the growth plate at the back of the heel bone. This area of the bone is very prone to injury in growing kids as it is the part of the bone that the Achilles tendon attaches to. Apparently the most common cause of this is hard impacts in sport, which given how much he is doing then it is not a surprise.

I read a lot on it at Podiatry Arena and the Foot Health Forum. In this thread, Severs Disease Treatment, there was some good advice.

This is what we going to do:
1. Cut back on his activity levels
2. use a soft cushioning heel raise (Severs disease heel cups)
3. Calf muscle stretching.

Will not worry about the doctor at this stage as from what I understand this is all that can be done in the early stages. X-rays for severs disease are of no use.