What does this mean

So there is a music event on near me, and my best friend asked me if I wanted to go a few months ago. The other day me and my boyfriend met up with his sister and she said she had a ticket which reminded me I needed to get mine.
I had planned to go with my friend all along and my boyfriend has planned to go with a group of his friends - no issues there?
So I’ve been excited and told my boyfriend that me and my friend have bought our tickets & he is now being horrible to me saying “you don’t have to be involved in everything why can’t I do stuff with my mates on my own”.
I have literally said NOTHING about me going with him and I’ve even said we don’t even have to see each other! I told him to have a good time with his friends and his reaction is horrible.

I shouldn’t have to justify why I’m going somewhere and I certainly shouldn’t have to not go just because we are both going to be under the same roof.

What does this even mean? Why is he being like this with me when I do nothing wrong?

So there is a music event on near me, and my best friend asked me if I wanted to go a few months ago. The other day me and my boyfriend met up with his sister and she said she had a ticket which reminded me I needed to get mine.
I had planned to go with my friend all along and my boyfriend has planned to go with a group of his friends - no issues there?
So I’ve been excited and told my boyfriend that me and my friend have bought our tickets & he is now being horrible to me saying “you don’t have to be involved in everything why can’t I do stuff with my mates on my own”.
I have literally said NOTHING about me going with him and I’ve even said we don’t even have to see each other! I told him to have a good time with his friends and his reaction is horrible.

I shouldn’t have to justify why I’m going somewhere and I certainly shouldn’t have to not go just because we are both going to be under the same roof.

What does this even mean? Why is he being like this with me when I do nothing wrong?

Sounds like an underlying issue - he said "you don't have to be involved in everything" and that he feels like he can't be with his friends without you. This is something to think about. Do you do a lot of things together? Are you quite often going to events / socialising with each other and his friends? Sounds like he isn't communicating how he feels with you, maybe he feels a bit smothered by you at times. This is something to speak to him about.

Nope. I don’t spend any time with his friends atall. When he’s with his friends he’s with them on his own I’m never there.
I’ve never been out with them or anything like that so that would be impossible to be an issue. Whenever we do things we do them together, our friends are a separate thing. We do have mutual friends who we see often but his group of friends , I never interact with unless it’s a small conversation when they’re round, or when we bump into them.