Your sexually active status does put forward a little concern when it comes to the possible diagnosis, but from your description it sounds like a simple cyst
which should subside without treatment (like most cysts do).
I would advise you to stop touching or irritating it, wear comfortable undergarments (preferably cotton) or avoid undergarments totally to prevent further irritation from friction. Avoid sexual contact of all forms and masturbation
as well (if you practice it).
Immerse your body in warm sitz baths several times a day and apply warm compresses to the region during other times. Adding some epsom salt to the sitz bath will also help.
If this does not subside on its own or worsens with the presentation of new symptoms within the next 7-14 days, then you will have to visit a doctor for a physical examination to provide a more accurate diagnosis.
Hope this helped.