How do I tell my boss I was ually harred?

There is this janitor at my place of work. I've been there a year and probably have only seen him like 8 times, but I all I've ever said was a simple "hello" and smile. I have recently lost a lot of weight and I've gotten compliments from men and women at work saying you look great and things like that. I've never felt uncomfortable. But last friday that janitor purposely bumped into me then he goes "You look reeeeeeeeeal good". Like I was a effing steak! I was so perplexed and shocked I didn't say anything I just start backing away and then he goes "come here" like at a club or something and I was like no and I walked back to my department. I was really shocked, scared, embarred and I didn't know how to tell my boss b/c he and I kind of like each other but we are still professional with each other at work. I know I have to tell him but I don't want to make him uncomfortable or think i would say something about him, BUT this janitor guy was just completely out of line..........any thoughts?