I agree with both above. I was going to say educate yourself on the topic, understand how common and (usually) unharmful it is before you tell him. Don't make it sound bigger than it is when you tell him. Obviously it isn't a nice conversation to have but if you handle it correctly it will be OK, especially if you drum it into him that you weren't aware of the fact when you had sex. Be understanding and supportive whilst explaining how easy it is to manage at the same time.:)
I'm not sure of your level of knowledge on HPV. That would be the deciding factor of when you tell him. You should tell him I believe, but not until you know a lot about the virus. Do you have high risk or low risk? What is the difference between the two? Which one concerns him more personally? How long does HPV usually take to clear? what are the risks of transmission? How about oral? What's the risk of oral? How would he even know if he had it? All these things and more are things you should know before telling him. remember, he just lost his virginity, so you can pretty much bank on him not knowing any of this. Without knowledge he stands a high risk of freaking out and catastrophising.
just my two cents
I was recently diagnosed with HPV as well and in a long distant relationship. My boyfriend and I have been dating for two years. When I was diagnosed I immediately told him. He was supportive and understanding and helped me get through it. I would have a conversation with him. He needs to know.