What do i do about this?

Ok I think my friends older brother likes me. I hung out with her last night, and we went to a bonfire. My friend, her brother, her brothers friend, and me were sitting and talking. He kept on winking at me. We were throwing little rocks at on another and stuff. We were hanging out. And he was flirting with me. And I was kinda flirting back. So what should I do? And also he is only a year older than me.