I'm mad at my boyfriend over a sandwich
Why would you be mad at your boyfriend over a sandwich?
I made him a sandwich for lunch, and he told me I've never made him something nice like that before.
I'm sorry that you are mad about this. You should probably get to know the likes and dislikes of your significant other. If you try to do something nice for him, maybe find out things that he likes that will make him happy, but getting mad at him is counterproductive.
Fuck that. I'm going to make him pay.
It is okay to be angry, but it is not okay to dump your anger all over your boyfriend because you didn't like the way he said something. Take his feelings into consideration here the same way you want him to take yours into consideration.