Welcome to HealthcareMagic. Most likely it is due to an infected or irritated hair follicle or a small cyst. since you are not sexually active, so there are no chances of a STD. Wear cotton undergarments, clean the area with savlon
and do not pop it. Application of Neosporin
cream and oral antiinflammatories like ibuprofen/acetaminophen
are also helpful. Also avoid masturbation
and intercourse till it is completely repaired.
Hope it helps you. Regards.