AITA for putting my nephew in his place after he tried to joke about my fluorescence disease?

My nephew (17) has band camp every summer. His parents had a conflict where they couldn’t pick him up this year. I got off work early and drove to pick him up. He hasn’t seen me without a mask since he was 8. I didn’t mention anything to him about picking him up because I didn’t want to confuse him. <br><br>When he saw me, he was shocked and asked me what was wrong with my face and arms. I explained what was going on. Then he asked if I could catch it. I was like no, it’s fluorescence disease and I’m getting better. Then he said, “Well, you’re glowing.” I told him that’s how we got the name. <br><br>He started making jokes about stop lights, traffic lights, and how I light up the night. I told him to stop but he kept going. I’ve never been a mean aunt but I do have a sense of humor. I decided to play along, at first I made a couple of jokes about how his eyes and teeth glowed in the dark when he smiled. He started to get annoyed and I could tell he didn’t like it. I then said stop lights and traffic lights. He got mad and I told him how I felt when he made those comments. He said they were jokes but I told him it was rude. He said sorry and I asked him if he could imagine being a 28 year old woman who’s fine and then finds out she has a fatal disease with no cure and how that would feel. I asked if he could imagine his friends and classmates staring at him and pointing as he walked by. He got quiet after that and has been quiet ever since. <br><br>His parents got mad at me for saying that to him. I told them that the boy needed to grow up and learn some manners. They said that I shouldn’t have used a disease as an example and I was being mean to him. I told them what he said to me and they said I should be more understanding.