Hello and welcome to HCM,
Nose bleeds especially in teenagers is common but causes which are dangerous should be excluded. You need to undergo the following:
1. Complete examination of the Ear nose and throat by an ENT.
2. Endoscopic examination of the nasal cavity
3. CT scan
of the nose and sinuses
and adjoining area
4. Full coagulation profile including testing for the clotting factors.
5. The treatment will depend on the findings of the above test but in general dont meddle with your nose and do not blow very hard. Also try steam inhalation.
get back to me with the test reports if possible or to your ENT
Dr Sriram Nathan