He lied when he said he was single

Okay so Monday this guy from work asked me to get drinks with him after and he was pretty cute. He told me he was single and that him and his gf broke up a few weeks ago. Long story short i slept with him and then the next day less than 24 hours later he told my friend he has a girlfriend. One of my friends thinks he’s calling me his girl since right when it was over he said “so what are we” but i think he played me and lied. What do you think? Also what should i do?