my boyfriend is really angry at me… because of league of legends

im 20(f) and my boyfriend is just a year older. ill call him seb. seb has a girl best friend abi and we have another mutual friend named alex (all fake names). seb and i started dating last year, hes a complete introvert and loves playing video games. im really really bad at playing games but i wanted to learn really bad so i could spend time with him. so the three of them just kind of let me play and tag along, because im sebs girlfriend. we started playing this game called league of legends. im really really bad at this game, and because seb plays in a different section he cant really help me. so i started playing a character that just attatches onto another player to shield. so i was playing with alex basically the entire game. its really easy and for a while everybody was pretty happy because we were moving up ranks (like getting better at the game). but today seb blew up on me and yelled at me in front of both of our friends in our call. alex and i play together the entire game and away from the rest of the team, and I used my own money so me and alex could match skins. skins are basically just cosmetic accessories for your character. I shouldve known better but seb got super angry at me and told me to refund it. i dont know what i should do.