I guess the event has already taken place and now, for some reason, it is bothering the persons involved. Nikah is a contract between a man and a woman, and no one else, to live together as husband and wife, and the society should know and acknowledge the fact. Two witnesses (minimum) accomplish that requirement and may vouch in case of any slender. As you have mentioned the scenario, the society already knows that the persons involved are husband and wife. Go and enjoy the life.
Dear forum members, I have been out of touch for a long time. I had been reading the posts, but could not write. I had to go through some very difficult economic situations and still dealing with it. I will try to contribute as much as I can.