How do I apologize to my boyfriend?

Yesterday I went to a party and my boyfriend since February was there too. I sat outside with my really good guy friend because he told me he felt sick. We used to have a thing but now were just good friends. I was just talking to him to make sure he was all good and stuff. Then he had the balls to kiss me and make moves. And knowing my luck, my boyfriend came outside with his friends. He got sooo mad at me, but I didn't do anything at all! He knows about how me and this guy used to hook up and stuff. My boyfriend started shouting at me in front of a lot of people from school. I haven't spoke with him since last night when it happened and he didn't want to hear me explain things. Should I still apologize to him? and How do I apologize about this? Should I just give him time?