My son ten years old gets pain in the back of the foot while walking right after he exercises and lasts for a few days then comes back . it has been like that since a year now but comes and goes . what could it be ?

Normal for 10 y o : I am assuming you are describing the Achilles tendon which is attached to the heel bone in the back of the foot. If that is the case Your 10-year-old son could be experiencing a growth spurt which is normal. stretching of the muscles are very important during this period of time. Physical Therapist can instruct properly on stretching or on the Internet