Boyfriend extremely upset and jealous

Last night, I hung out for an extra few hours with my friend N and my gay friend M until midnight. We sat on the ground and played board games and talked for a while. My boyfriend got super upset that I wasn't texting him back fast enough and that I was ignoring him. I wasn't texting back a lot because I was with my friends and its rude to constantly be on my phone. What should I say to him? What did I do?