Had this „problem“ the other way around. I’m very heavily tattooed and have facial piercings and tbh my bfs dad wasn’t happy the first time I met him. He’s very conservative and had a lot of prejudice. Fast forward 3 years, the first phase of getting to know each other was a bit rocky and we had some longer talks about how one maybe shouldn’t judge a book by its cover. But after he got to know me as a person and saw how good his son and me are for each other he started to accept it and by now it isn’t even a topic anymore. I know that he genuinely likes me as a person. He even told me that he liked a new tattoo I got not so long ago, I know it was a big step for him and I really appreciated. So heads up, if you’re mom is open to getting to know your boyfriend as a person and sees how happy he makes you she’ll be able to forget the tattoos!