It is inevitable that at some point your child may pick up an injury, whether it is through diving or not.
Most people consider the first port of call to be their GP. In the majority of cases a GP will recommend rest, even though the problem could re-occur when activity resumes.
As a sports club, we would advise you to find and use a chartered physiotherapist with an interest in sports-related injuries. In the case of children, it is particularly significant that their changing bone density and maturing/joints/musculoskeletal system is fully protected. Unfortunately, resting and taking pain relief is not the long-term strategy for getting back to full fitness.
We appreciate that treatments can be expensive but they are invaluable. If you have divers training 5 or 6 times a week, you may wish to look into insuring them with a medical package that covers a physio should the need arise.
We would also advise any diver with a heavy training schedule to perhaps also look into occasional sports massage as part of their ongoing health regime.
IF IN DOUBT SEEK ADVICE!