Thanks for your query.Based on the facts that you have posted it appears that your son has developed Epididymitis
an infection of the epididymis of Right Testicle.
However this can be confirmed only on clinical examination by a qualified Surgeon or Urologist
and ultra sound
scanning of the scrotum.
Take some antibiotics like Doxycycline along with some antiinflammatory medication like Diclofenac
twice daily for a week.
get prescription of these drugs from your family Physician.