I think it's probably normal, but I've read some threads about similar stuff on here and people did show concern, so I'll just explain.
Two and a half year old often touches down there when not wearing a nappy or at nappy change and says ' don't touch it '
I don't in any way, just to clean and put cream on. I think it's possible that her dad has told her not to touch there when she's done so with dirty hands perhaps during a nappy change.
I am guessing that's where it comes from, rather than something happening at nursery ? It's hard to say. Or am I being completely crazy to be a little bit curious about why she says that ?
Did / do your kids say that? It's probably completely normal.