Should my bf get mad at me over a sandwich?

So my bf got mad at me over a sandwich from mcdonalds it was a fish sandwich yall know how small they sandwiches He had already ate a meal from sonic it was a breakfast barito with tots I did not eat hardly any accept a lil bite ofhis burrito bc i really dot like them plus i also had to go to the dentist. so after the dentis we went to the movies i had not ate all day so we went to mickey d's and i got a small frie and a fish sandwich i offered my fries he ate some of those and i i gave him the rest of what i did not eat i said did you want some of the sandwich he was like yea but just save me some and i did but when i offered he was like are you givin me the whole half bc im a go in eat the rest no i did not want to give him the whole hal of what was lefti was still hungryand told hi so i started eating some more and was just gone save him the last bite and he got pissed and called me selfish after he had damn near a whole meal this morning by the way i did not eat bc i went to the dentist i know this is stupid to be asking but am wrong for saving him a bite he said it was not abt the sandwich it was bc i was selfish.