Consult with and retain a lawyer. If you are contacted by the police, direct them to your lawyer. An experienced, competent criminal defense lawyer should know how to "run interference" for you with the police, and possibly even head off a criminal accusation. Even if he/she is unable to do that, there is no reason for you to talk to the police. Their job is to establish probable cause without your statements. If they can't do that, then you can't be charged. If what you are saying is correct, the "other guy" won't have any bruising or other signs of assault, and without that, all the officers have is his word, and no physical evidence. You do not need to assist the police by saying something which might be misconstrued against you.
Further, should you be charged, your attorney may be able to discuss your version of what happened with a prosecutor, by making a special kind of proffer which cannot be misconstrued or used against you.
Ultimately, if you are charged with any criminal offense, you may tell the court what happened at the appropriate time, from the witness stand.
I'm licensed in CA only, and you should always check with local counsel. Having said that, anytime someone suspected of criminal conduct speaks to the police, thinking they'll win law enforcement over to their viewpoint, things rarely turn out that way...If there are any additional witnesses other than your wife, get their names and contact information, to preserve in the event anything comes of the incident. The statement that you pushed him is an admission which can be used against you, even though you're thinking you did it in self defense. If the matter really is as minor as you've stated, I can't see law enforcement spending time and resources on it (but that's no guarantee they won't) - and it certainly doesn't seem serious enough you'd be looking at being arrested for. So, if you are contacted by police, be aware of the fact that "anything you say can and will be used against you in a court of law". If you have an attorney, all questions should be directed to him or her. Good Luck & God Bless.