Getting a guy friend back

I once, shamefully, kissed a friend when I was in a relationship. I was deservedly dumped. There doesn't seem like anyway I will be able to get my boyfriend back but now the dust has settled a bit I wonder if I can get my guy friend back. He briefly kissed me back and I think realised what he was doing and stopped it. Since that happened he has been very cold, I hardly see him and he is blunt with me. He will either avoid our social group events or turn up and not speak to me at all. I don't know why he is behaving this way as he is single and hasn't done anything wrong. It was all be. I just want to know why he has gone cold and if there is anyway to restore the friendship. We've never spoken about it and I don't want anything more than friends.