I think I taught my nephew a bad habit (update)

I talked to my nephew yesterday. Basically, I brought pizza to my sister's house as an apology and sat with him while he ate. I told him that jokes are only funny when 1- everyone else is having fun too, and 2- you're not bothering or hurting anyone. He seemed to understand, and well, my sister also scolded him quite a bit, so he doesn't seem very keen on making jokes for a while. I guess the matter is settled. Just in case, I apologized to my sister, and she told me to forget about it, so I think that's it.