Grain of salt and all that, but he claims he didn't know it resembled a Nazi symbol and that he plans to get it removed. Not entirely sure how much I buy that answer, but his explanation of how he ended up with it seems like it could be plausible, so... Idk.
Also apparently Bernie still stands by him too.
https://www.politico.com/news/2025/10/21/graham-platner-tattoo-nazi-00617686