It i kissed someone who was hiv positive with a cut in my mouth could the virus pass to me? does it take a lot of blood or just a drop?

No risk, no worries: Kissing never transmits HIV, or so rarely the risk can be ignored. (There litererrly are only 2-3 cases known in the whole world over the course of the 40 year HIV/AIDS epidemic.) Cuts in the mouth are very common, but still no cases. The amount of blood that might create a risk isn't known, but it would at least have to be a very large amount, with blood all over the place. Don't worry about it!