Thanks for your query. As said by you probably it is musculoskeletal pain
due to trauma. Try some analgesics like ibuprofen
him and give him some rest. If still he doesn't improve then he needs to be shown to an orthopedician. He will examine your son and he will order an Xray only if needed.
Don't worry he will be better by a day. But do keep a watch on him and if anything worsens or persists don't hesitate to show to a doctor.
Dr. Balaji Chinnasami MD
Assistant professor - Pediatrics