Should i tell him i kissed another guy?

The moral answer is Yes tell him. The real answer and the most realistic is NO! For starters Andy just now told you he liked you. You are not commited to him and it was a kiss. If you felt something for the other guy I would say yes, tell Andy you can not be in a relationship with him right now, but you said you did not want that with this other guy. It was a kiss, you did not have sex with him and even if you did, you are not yet official with Andy. Put it behind you. It is in the past and if you open it up before the relationship even gets started you are going to destroy something for nothing. You would not kiss this guy again, and would not have then if you had not been drunk. Now from here on out you will have to watch yourself and your drinking to make sure you dont cross a line, once you are official with Andy, stand by it or end it. Tell the other guy that you are starting a relationship and you are sorry if he got the wrong idea. The end.