My son has noticed that sometimes he’ll get an erection. He doesn’t stim or seem to have noticed a correlation between touching it and an erection, but I’m sure he’ll figure it out soon enough. As you said already, it’s totally normal and it’s nothing at all to worry about. I wouldn’t draw any attention to it now, by asking her what she’s doing etc, if it’s a behaviour that isn’t happening elsewhere, throughout the day etc.
My son is ‘exploring’ himself. I tell him if he wants to touch himself he needs to go in his bedroom and to stop if he isn’t alone. I found this website to be helpful. https://www.healthychildren.org/English/ages-stages/preschool/Pages/Sexual-Behaviors-Young-Children.aspx#:~:text=When%20these%20behaviors%20happen%2C%20it,that%20in%20a%20private%20place.%22
It's totally normal and developmentally good behaviour. There is plenty of literature about it if you're interested. Do not worry, all is fine:)
Thank You all for replies, always reassuring to have a listening ear on here ❤️
I have litte boy and he touching down there often then doing like some movemnts too. He do get like shy too when I see I ask him what you doing? He said nothing. He do ask me or my partner why his (u know what) getting big ? Well wasn't expecting to have that question in his age 🙈