My boyfriend kissed me on the cheek today, and I was just wondering...?

Ok, so we were hanging out at school after cles got out with his best friend and his best friend's girlfriend. I was kinda zoned out then out of nowhere he kissed me on the cheek, so I just looked at him and gave him a big smile. Then the other girl with us was like "dissed!" I was wondering if when he does that I should kiss him back on the lips? Because that's what they made me feel like I should have done. Hmmmm!