Sore throat is usually not a symptom of Herpes or an STD that I know of... Give it a little while longer and if it gets worse see a doctor.. Thats alll you really can do.
your throat wouldn't be sore that quickly from a std. odds are it's completely unrelated to you licking his penis.
If you two are starting to think about sex together, even oral sex, it's time to have some talks about it. Have you talked about if he has had other partners and what your past sexual history is? Have you talked about if he gets cold sores or if you do? Have you talked about using condoms for oral sex and genital sex? What about birth control?
www.iwannaknow.org is a terrific website for teens for std info, condoms and birth control. Might be worth the both of you checking out before this relationship progresses to a more intimate level.