The best advice would be for you to contact the prosecuting attorney and tell him that you do not wish to cooperate in the prosecution of your friend. No prosecutor wants to have an uncooperative witness at trial. Let the prosecutor know if you were the one who started the fight. The defendant may be able to assert self-defense and the state may learn that they no longer have a slam dunk case. Some prosecutors will tell you that it doesn’t matter if the victim wants the case dismissed because they represent the State of Minnesota, and not you. If you are sent a subpoena in the mail, you will be asked to sign the back of the subpoena and acknowledging receipt of it. If you don’t acknowledge receipt of the subpoena, the service is ineffective and the prosecutor will have to send a process server out to your house to personally serve you with the subpoena. That costs the state money they may not want to spend.