Boyfriend makes fun of my arms

So my boyfriend and I have been together for about a year and when i wear short sleeves he’s been teasing my arms and making fun of the fat on them because i’m a little chubby. I’ve told him it bugs me but he just says he thinks it’s cute, i’m 5”2 and 125 pounds do u guys think i should start a diet, or how would u deal with it?

THANKS TO EVERYONE WHO REPLIED

I wanted to add my boyfriend doesn’t make me feel insecure about my weight it’s more of a personal issue. It just irritates me that he teases me even though I’ve mentioned how much it irritates me he takes it as a joke, I’m not sure how to make him take it seriously?