I screwed up and told a lie to my boyfriend. Please advise me on how to work this out?

Last night my boyfriend and his friend got into an argument over something that happened in a video game that resulted in my boyfriend being extremely irrationally angry with his friend. (ignoring phone calls etc.)

We’ve been together for a year and I’ve also become friends with his friends so I really hated seeing them fight and having his friend of 10 years so upset about it. His friend (whom, I have a platonic, brotherly relationship with) asked me out for a drink with some other friends to talk about how we could smooth it out between them. We were not alone at any point during the evening.

I was trying to help smooth things out between them but I knew my boyfriend wouldn’t understand so I told the only lie I’ve ever told him and said I was getting drinks with my other friend. Well he found out and now he’s EXTREMELY angry. At first he accused me of cheating (I would never) and says he might never be able to trust me again and that his friend since college is no longer his friend. :’(

I’m so upset over this and have tried apologizing to him many times but he just won’t listen. My intentions were good despite being a little naive to think it wouldn’t backfire horribly. I know I was wrong to lie to him and I didn’t mean to hurt him so please don’t come here just to bash me. I’ve never been unfaithful to him and want him to understand that I’m sorry and that my intentions were good.