hello drak**** thanks for your question You are 15 and never had sex, and you have developed a little bump on penis, and also under your head. Pal as we all know that HIV (AIDS) infection spreads by either Sexual Route, Transplacental, Parenteral route (contaminated needles, razors etc), or by contaminated blood transfusion. Similarly STD spread by having coitus with infected person. AIDS usually don t present with the symptomatology you have described, main presenting features are persistent infections, diarrhea, cough etc. probably the blister on your penis is due to poor hygiene which resulted in blockade of sweat glands and resulting in infection. Don t worry and maintain good hygiene. If your problem still persist then discuss with your parents, as you have not done anything wrong. thanks and kindly rate. :)