Suggest Treatment For Pimple On Labia Majora

Hi! I am Fiolla 21 years old, I'm still a virgin at this age. I just want to ask this. I have this large bulgy pimple on my labia majora.. It is not painful although when you press it I can feel a bit pain on that area. It is swolen for a week now. I am wondering what it is and what is the cause and the possible treatment for it. I am afraid that it is a boil or it will possibly become an STD although I never had sex with anyone for my entire life even penetrating it with foreign material. I never seek help for medical personnel. Please answer me. Thanks in advance.