So I screwed around with my friend.?

I'm a guy and she's a girl. We had this movie marathon and then crashed on the same couch. The next morning I found my hand on her and couldn't help myself. I started and she enjoyed it. Then she directed my hand down and I rubbed her through her pants for a while and she did the same for me. She tried to do more but my guilt got the best of me because I have a girlfriend, so I stopped. She went home shortly after and we haven't talked since and it's been a week. Things are horribly awkward. I don't plan on telling my girlfriend about it because it was a one time mistake(not interested in advice on that) but my problem is how do I fix things with my friend.