Need advice!

My partner and I were having sex just a bit ago (130am) and my 13 yr old heard it! He started to throw things and I asked him to stop. He yelled asking if we can be quiet because he’s trying to sleep. This is the first time it happens that he hears us or that he says something. Im terrified. We weren’t being vocal it was more like a smacking sound and we usually are super mindful and quiet. I guess we were too into it today.

How do i address this with my child?