5 year old touching self.

I have a 5 year old boy and it's been a few times I've seen him touching himself under covers. Nothing to the extreme, just touching. And Ive actually called him out to go wash his hands. Today I caught him on his bed completely naked. And he was embarrassed as I walked in. How do you handle a situation like this? What do you say? Is it normal for boys to start getting more curious with their bodies at this age?