I would barely call this a risk. First of all you don't know his status, and chances are he is HIV-. Second you did not have prolonged unprotected intercourse with him leading to ejaculation. If you are concerned, maybe you both should get tested with a 4th generation DUO test. If that comes back negative on him, you are essentially in the clear. If you want to get tested, do it after 1 month. When it comes back negative accept those results.
PEP is usually recommended when the risk is significant, that is unprotected vaginal or anal sex with a confirmed HIV+ partner. However you should consult a doctor specializing in infectious diseases to evaluate your risk and decide
If head of his penis was entered in a way that you could not see it, there is a slight risk due to possible precum. Your risk is there but not significant because his status is not known and strong chances are, he may not be an HIV+.
It is good that you do have concerns about unprotected sex.. only a condom is the best friend of a woman, not her boy friend. Next time, unprotected sex only between you and your mutually committed monogamous partner, for rest of the world, no contact without a protection.
You may get yourself tested for HIV Duo 4th generation after 4 weeks of the exposure, collect your conclusive report and move on with your life