thank you for your query.
Teenagers are very prone to infections and inflammations in the genital region because of immature hormonal
As you are not sexually active, I would not suspect a sexually transmitted disease
Rarely, such infections can be picked up from common washrooms or shared linen, however it is very rare.
What you are having sounds very much like a yeast infection , which could cause such sores.
please consult a gynecologist, and do not self medicate yourself, as some conditions could flare up, leaving you with permanent damage.
Maintain strict perineal hygiene.
Keep private parts dry.
Do not touch them, rub them or clean over vigorously.