Can I fight the resisting arrest charge?

I was charged with resisting arrest at walmart after being escorted out for criminal trespassing. I already knew I was not supposed to be there but I did need groceries and I had no vehicle to drive anywhere, nor was there any other markets within 5-6 miles. While being escorted out I did everything I was instructed to do and I complied in every fashion. While standing at the front of the cop vehicle beside the driver side headlight the officer asked me to turn around, leand over the car, and put my hands behind my back. Now to clear up some things I have only been arrested with handcuffs once in my life and it was a PI where, even while intoxicated, I did not resist arrest and complied with every request even a body search. So when the cop asked me to turn around, lean over the car, and put my hands behind my back I wasn't sure what to expect. He then put the handcuffs on starting with my right wrist, once I felt the cold steel I flinched and turned around because I wasn't sure what was happening and the officer never told me he was arresting me prior to doing so. After that happened he proceeded to push me against the car and while doing so he nicked his right hand inbetween his thumb and pointing finger. He told me I was being charged for resisting arrest there after. I am not sure if flinching would be considered ressisting arrest in Texas, especially if you don't whats about to happen to you when the cop tells you to turn around and lean over the car. I figured he was going to do some kind of search but I really just did not know what was going to happen. If you have any advice as to wether or not I would have a strong case to take to court I would really appreciate you knowledge and experience in the matter. This happened in Hildalgo county last summer (2011) around July. They are also offering me differed adjudication and are telling me that if I do it the charges will be exponged from my record. There are two problems with that. One