This will be a very weak case for prosecution unless there is corroborating evidence to go along with the confession because without your voluntary admission the officer had no knowledge or evidence a "crime" was ever even committed. Things like:
-did you also report the harvest on the azgfd big game survey.
-social media with photos of you and the deer which are dated.
You might want to find out if the officer recorded the conversation in which you made the voluntary admission. If there is no corroborating evidence, no recording of your admission, and you don't testify against yourself in court, then there is no evidence for a court conviction. You probably should consult and attorney to confirm some of this because there is potentially at lot at risk for you.
I have been hunting Arizona for more that 40 years. In that time I know of 3 incidents where the wrong sex of big game animal was shot by mistake. In all 3 cases the person who shot the animal called the azgfd operation game thief hot line and reported the themselves. They then met a gfd officer and presented them with the animal. In all three cases, the officer took the animal and their tag. They were thanked for their honesty and told their hunting season was over for this year. The meat was used to feed homeless people or wounded wildlife in recovery. The third incident was actually this year. Someone I know shot a doe thinking it was a spike. She took the meat to gfd headquarters. She was an emotional wreck. Bawling and swearing she would never hunt again. The officer actually tried to convince her took keep hunting. He thanked her for her honesty and told her this incident would make her a better hunter in the future. He then took her on a tour of their facility and showed her the bobcats they were going to feed with the meat she brought them! An excellent example of community police relations.
Sorry you have to deal with this.