How risky is kissing?

I’m a 17 year old slowly falling for someone who has just told me that they are HIV+. Both the decision to stop the relationship from happening and to keep going seem to be wrong. (Either I put myself at risk, or potentially wreck his emotional state.) I don’t even know who to listen to about the risks though. Some say if I kiss him, I’ll get HIV and some say I won’t unless I have open cuts in my mouth. Just how risky is all of this?