I have a work problem with my MANAGER help!

so I've been working at this store for alittle over a month now and my one manager is hitting on me at least I think so. I don't know what to do he's atracttive and everything but he's 23 and I'm about to be 18 and I don't know what to do.Should I flirt with him back? Should I tell him to stop I have know clue please help.