Moms of little boys

I wasn't quite sure where to post this but I just had a question for the moms out there of little boys. So my 3 year old keeps getting erections. He'll say "look, mommy, my pee pee is big". I read on the internet that it's completely normal. However, I'm curious to those who have been through this, what you said to your child. I just say, okay okay, just leave it alone. I don't think that's that's what I should say. Any suggestions?