What Causes Frequent Pimples On Penis?

Hi. Need some advice........ My boyfriend and I have been together just 2 months and have not had sex yet. He was upfront with me and advised me that he has had genital warts approx. 1 yr ago (last outbreak) and that his ex-girlfriend was dx'd with hpv. Lately, he's been experiencing what he describes as an occasional very painful pimple on and around his penis. Sounds like a genital boil to me the way he describes it. My question is, do you have any thoughts on what he could have and is there anything, other than using a condom, that could prevent 'me' from getting infected if we decide to have intercourse at some point? His doctor does not believe he has hpv and is unable to tell him what he has.