Should I feel guilty about this stupid joke?

[MarkSummers]

I'm home for the Jewish new year, Rosh Hashannah and my mom is busy making dinner for our guests coming over tonight. The phone rings and I answer it and it's one of my mom's friend who asks if any of the food she's making has nuts in it (presumably because someone she's bringing is alergic?).

I ask my mom and she says no there's nothing with nuts she's making. Her friend asks, "You sure, absolutely nothing?"

I relay to my mom, "You sure there's nothing mom? What about that nut salad?" My mom laughs as she picks up on my dumb joke and says that there's nothing with nuts. So I tell the friend that there's absolutely nothing. She says, "Wait, what about the nut salad?" I tell her that it was just a joke but she doesn't seem think it's funny.

Should I feel bad or was this harmless? I guess if you're alergic to nuts it's not very funny.