Hello sir im having some red pimples on the center of my penis most likely after masturbation .its been there from few months but it was more now its less pimples please replay to me im really worried could it be an std?

Not masturbation: Masturbation doesn't cause any kind of penile skin problem. "Red pimples" present for a few months is unliklely to be an STD. A possible exception is molluscum contagiosum, a minor viral infection often transmitted sexually in young adults. (Google it to see photos and see how they compare.) Of course you can't get any STD if not sexually active. Stop worrying and wondering; see doctor or clinic.