my cousin walked in on me and my boyfriend

Yesterday I was having sex with my boyfriend well not sexy sex just lifting up my skirt and putting his dick in me we were being sneaky cause his sister and mum was home. After awhile we finally left and went to his bedroom we were finally horny and unclothed after 30 minutes his sister walks and screams then his mum comes in. I was so embarrassed and I put my clothes on and went home. I haven't talked to him since and I don't want to come over on Fridays ( it's when I study at his house) what do I do. HELP QUICKLY