I think ive ruined my friendship with my cousin

Ive been close friends with my cousin for as long as i can remember we talk almost every day and theyve always been the first person I’d go to when something happened.
A few weeks ago I started to talk to this one girl over text we got pretty close over time. We werent anything more than text buddies maybe a bit intimacy over text but thats all but then one day i talked with my cousin and he said that he met a girl a fun one too. Naturally i was excited for him as he were single for a long time and he kinda needed that relationship(i yet didnt know she was the girl i talked to over text) but then there was a family party where my whole family meets up for two days and sometime when we were there she called me when i was sleeping on the couch and my cousin were on the floor sleeping and he mustve seen the number on my phone because in the next morning he got so effin mad that we almost started fist fighting and the rest of the day was super akward so i left around noon to rest from all the madness. A few days later i tried to text with my cousin and reason with him i tried to explain that i had absolutely no idea that she was the girl he was with and ofcourse he didnt believe me and now i have no idea what to do. I dont want to lose my friendship with my cousin over something so stupid. We have been with absolutely zero contact since. This happened two weeks ago please help me(im sorry for grammar errors etc im not a native english speaker)