I got a small greyish brownish pimple. It looks like a wart, it doesn't hurt nor itch, I was sexually active a week ago?

Penis bumps. Penis bumps can be many things. Some STDs, some not. Only general advice can be given without a photo or physical exam. Top 2 photos are non-STDs: Fordyce spots (sebum which can be extricated by M.D. or left alone), Infected hair follicle (plucked and kept clean). Bottom 2 photos are STDs (HPV and Molluscum) to be evaluated by your MD so s/he can rule out other STDs and council you for prevention.