Should i tell my fiancé?

Im at my friends house for my 21st. And her boyfriend lives with her. And her and i went to pick him up from work. And as we were walking through their house, he slapped my butt. He said it was for my birthday. But it still made me feel weird. Anyway should i tell my fiancé that? I mean it wasn’t sexual or anything. And i know that if i tell him, hell hate him for it and will always have a problem with me coming over here. He’s super protective over me and doesn’t let things go when people do stuff to me. So i already know that he’d never let it go especially if another guy is touching me. Am i looking too much into this? Should i just let it go? Or tell him and have him hate hime forever.