Hi Heba, Welcome to HealthcareMagic Forum.
Your son is having epistaxis
and there are various causes to this. Kindly don't as it common in this age group, get him examined by a ENT Specialist
to rule out the exact cause for his nose bleeds.
The treatment will depend upon the cause.
When ever he has a nosebleed episode make him lie down on the edge of his bed with head dangling down and press and release his nostrils alternatively, for 5 to 10 minutes until the bleeding subsides.
Give him healthy nutritious balanced diet.
I wish him Good Health.
All the Best.