This past Saturday, I made out with a girl. The make out session lasted for a while and I had a canker sore or somekind of sore on my bottom gum at the crease between my lower lip and gum. If the girl had HIV, should I be worried and what are the risks of transmission this way?

there is only one case that showed an HIV infection from deep kissing, but bothe people involved had AWFUL dental problems. and they can't really prove that all they did was kiss. saliva has an agent that kills HIV so it is very hard for it to live there, any open sore is a way for HIV to enter the body but saliva is NOT a way to pass it, i would NOT worry at all.

No you should not be worried about HIV at all. It is very difficult to catch, the virus is so fragile. Put your fears to rest and just be safe, and happy. Those two come hand in hand, ya know...you are happy when you feel secure and safe, and 'making out' should not make you fear HIV, you should only feel love (or/and trust) I can't say that there is any real definitive guard against HIV, but it is very difficult to catch. Really, the sad truth is that most men (especially men who contract it heterosexually) do so from long-term partners. You are fine, relax a bit. Your encounter is safe. Just worry about finding a girl you love enough to talk about sex (and sexual history) comfortably, and with out judgement. Again I must reassure you Not to bother yourself about the possibility of contracting HIV. Really just not possible--even with a very, uhm, intimate make out session. :-) You are alright.