Go right up to them and clear your throat and say something like, "Excuse me, I need to get to my locker." That's what I would do. I wouldn't even think that kissing in the halls would be permitted since it usually isn't.
I always feel guilty when I don't go to a class when I'm only slightly not feeling well. Like today when I decided I wasn't going to my film class because I wanted to make sure I didn't have some sort of fever spike again since when I'm sick it always gets worse in the evening, and as soon as the time that I would normally go to class rolled around, I was feeling guilty about not going.