Transgression against someone's right

Assalamu Alaikum. I am really scared about this. The thing is that Me and someone else (a fellow) transgressed against someone's right. He gave me an idea and i just remained silent and he did the transgression (so i am also involved in this). Now after being guided it has come to my mind that i should apologize to the person whose right we transgressed against and also restore his right in some way if possible but by telling him that we did such a thing would expose the fellow with whom i trangressed . **So should I hide his sin or apologize to the person by exposing him?**