A naked encounter with my brother?

This morning i was in the shower and forgot to lock the bathroom door...and long story short by brother entered while i was getting out of the shower. He just kept staring at me for a while and then he left the bathroom. He obviously didn't know that I was there. During breakfast and lunch he looked at me sort of shyly and werid like be was very embaressed about what happened. I have a very close relationship with my brother but today he hasn't said a word to me. Should I talk to him, and what should I say? by the way i'm 17 and he's 19.