My best guy friend and I made out and now he's ignoring me.

Yesterday I was cuddling my best guy friend in front of my other friend who has a major crush on him. After she left his house we cuddled for a bit longer and then started making out. He kissed me first. We promised each other we wouldn't tell anyone, including our best friends and continued to make out until his mum texted him saying for us to meet him at the park a few blocks away. The worst part is, I tell my friend everything and I can't tell her this because she likes him. I enjoyed and the guy knows it. He also knows I used to have a massive crush on him. It was also my first real kiss. I'm terrified that my friend will find out about it and be angry at me. I know I won't tell her, and he won't tell her, but I have a feeling things will be different between the guy and I and she will be able to tell that something happened. A few of my friends are in his classes and one told me that he was really withdrawn and quiet in class, which is unusual because he's usually really loud and attentive. I spoke to him about it, and he told me that it was a one time thing and we shouldn't tell anyone, but he didn't sound like he meant it and he sure as hell doesn't act like it. He has been ignoring me all day and avoiding me like I have the plague. I don't know what's going on, and I don't know what to do. Help.