What is a pre-trial and will I get to talk to the judge about my case, and possibly get judgment then and there?

Do I need a lawyer for the pre-trial? I had a traffic violation for 12-6-12.4 for careless driving. I missed the sudden stop of the vehicle in front of me after the intersection light had turned green, and did cosmetic damage to her car. Mild injuries were reported from her, and my insurance has fully covered her claims. I went to the arraignment hearing at municipal court, prepared to plead 'no contest.' The first thing the judge did when it was my turn was tell me this charge carries with it a potential jail time of 90 days and a fine of (I don't remember). I panicked, still offered 'no contest,' and the judge told me that I would be waiving my rights. I said this was all new to me, my accident was an isolated incident, and didn't know what to do. She suggested I change my plea to 'not guilty,' which I did, and now have a pre-trial scheduled. I was not driving recklessly, I was navigating rush hour traffic in an unfamiliar city (I live an hour away) and had looked away at the traffic intersection at the wrong time as the car in front of me was stopping short, resulting in collision. It was an honest mistake. One that nevertheless I do feel bad about the situation and grateful that no serious injury was caused. It is an isolated mistake in an otherwise 20+ year perfect driving record. I feel I could have a case in pleading not guilty but I'm still willing to plead 'no contest' if it will just end this and not result in jail time. Please help!