My boyfriend's penis has some small pimple-like around the back of his penis head. is this a sign of herpes?

Depends on bumps: If pale/pink and frim, likely are pearly penile papules, which are harmless. See: http://pppremoval.Hubpages.Com/hub/pearly-penile-papules-ppp-removal-treatments -- if red/pimple-like or ulcer-crater like--could be herpes. If in doubt, or if not trying to get pregnant--use condoms. Also, can send him to his dr for check to be sure is not warts (not likely by description).

Herpes: Herpes usually looks like a blister or fluid filled bubble, or a red sore. It is often painful. So maybe - or it could be other infections or even just an irritated spot. Can you ask him about it? Be cautious until you are sure.