Hello dear,
The symptoms as mentioned in your post can be attributed to musculo-skeletal injury .
X ray of the affected leg will be helpful to rule out any fracture or other pathological causes.
Symptomatic relief can be obtained by
heat therapy, application of analgesic &
muscle relaxant gel, intake of analgesics like
Diclofenac (to be taken after food) +
Pantoprazole (to be taken 30 minutes before meals).
Supplements of Calcium & Vitamin D can be included in diet which will help in strengthening of bones.
Physiotherapy exercise will also be helpful.
If symptoms still persist, kindly consult an Orthopedician for proper clinical examination.
Also he should maintain adequate hydration & nutrition status, take proper rest and avoid stress.
Wishing your son a Good Health.
Take care.