It sounds to me like you're not clear really as to what exactly transpired and what contact was made.
If that is the case, I would suggest you err on the side of catuion and obtain emergency contraception. Really.
It's not a scolding, but do understand that "things" don't lead anywhere. We choose or choose not to act. Y'all chose to do things without thinking. It happens, but it doesn't have to -- you control these scenarios.
After you handle the panic -- which, btw, should include STI screens a couple months down the road -- and before you get intimate again, I'd suggest you both have a talk, make limits, and get the things you need to have sex safely and responsibly.
if you don't know what those are, look around the site here. You can start right here: http://scarleteen.com/sexuality/readiness.html
Editor and Founder, Scarleteen
My epitaph should read: "She worked herself into this ground."
-- Kay Bailey Hutchinson