What Should I Do?

Hello, everyone so I have a bit of a situation and I don't know how to handle it. I work at a retail store Homegoods and every thing is all good and swell but (side note: I'm 18). There is this guy and he likes me (he has told me multiple times). and that's fine I'm not asking because of that but he's 30 years old. I didn't find it weird or anything but then he got to attached and started hugging me and one time kissed me on my neck. I found it weird and immediately showed my discomfort. He isn't a bad guy at all he's nice and knows his limits but how do I keep it from escalating? I'm worried maybe I'm giving him the wrong idea... I don't want to seem like a flirt but I don't want to be a bitch either. I don't know what to do.