What Does Recurring Pain In Groin Post Treatment For Groin Injury Suggest?

My son aged 13 yrs got hurt in his groin region during long jump session where the rod hit him. I took him to a ortho doctor who told us to get MRI , X-ray and blood test done. After going through the reports he gave him paracetamol tab for 3 days and advised rest for 15 days. After 10 days the pain and stiffness disappeared and he started going to school. This again resurfaced once he started playing kabbadi and swimming in school. The doctor again told him to take rest. After few days he was ok and it has resurfaced. Kindly tell me what could be the reason?