Read Wilson v. Blankenship, 163 F.3d 1284, 1290-91. Then .....
Ask yourself, do I really want to go it alone?
The Judge Cannot Help You
Remember, if you represent yourself the same standard as a professional attorney is applied to you. The Judge cannot give you assistance and maintain the required courtroom decorum of being fair and impartial to both sides.
All Rules Apply Equally To You
As pro se, you'll be held accountable for having the same information about the rules of court, rules of law, and rules of evidence as an attorney who has years of experience handling cases. The judge would be right not to give you any breaks. If you file a brief or motion to dismiss incorrectly without following either or both of the procedural or substantive rules it can and most likely will get thrown out of court.
What You Do (Or Don't Do) Can Mess Up Your Appeal Rights
If your case ends up going south with you losing you cannot appeal based on not having had done things as well as an attorney. Every Judge I know warns pro se parties that representing themselves is not a good idea. The judges have a reason for doing this; IT IS A TERRIBLE IDEA
Refusal of Counsel
If the person refuses court-appointed counsel in the government's attempt satisfy the Sixth Amendment right to counsel in a criminal case that person has no alternative and is not able to argue denial of the right to access to the courts. Wilson v. Blankenship, 163 F.3d 1284, 1290-91.
I would echo the advice above. A simple assault conviction can result in up to 6 months in jail and $1,000 fine. Assuming you have a clean record, imprisonment is unlikely under the circumstances you described, however, you should be aware that the possibility exists.
It sounds like you intend to claim self defense. Self defense is more complex and nuanced than many people realize. I would strongly recommend speaking with an attorney about the specifics of your case to evaluate the merits of a self defense claim. At the very least read the self-defense statute, N.J.S.A. 2C:3-4. One of the main elements you will need to establish is that the force used was reasonable and that that it was immediately necessary.
If you insist on representing yourself, as is your right, I would strongly urge you to visit the court where your trial will take place and observe how that particular judge and prosecutor handle trials. Procedures can vary greatly from judge to judge, especially in municipal court. Best of luck.