I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear about your situation.
The worst outcome in a criminal case is typically reserved for individuals with extensive criminal records. The odds of you getting the worst outcome are extremely low, even if you do absolutely nothing. However, you have the ability to try to negotiate with the district attorney to achieve an outcome that you feel is acceptable. That might mean paying a low fine, or serving a term of probation and doing community service, or something like that.
You also have the ability to plead not guilty, request a trial, and make the district attorney prove beyond a reasonable doubt that you acted in a disorderly manner. They can't make you testify against yourself, so they'll have to call the other driver to testify against you. You'll be able to ask him questions to prove that he's lying. And if anyone else witnessed the incident, you can bring them in to testify on your behalf. With that said, a person usually gets a more favorable outcome if they plead guilty and negotiate a deal than if they are found guilty after a trial. You have a right to have a local attorney assist you in negotiating if you want one.
If you have any questions or concerns about what I've written, please reply so that I may address them. If I did not address the specific thing that you wanted to know, it may not have come across clearly to me, so please restate that question. It's important to me that you are 100% satisfied with the service I provide. Otherwise, please rate my service positively so that I get credit for answering your question. Thank you.