How to defend the wrong F.I.R

I am working as the site engineer in southern railway and I have 5 working site at a time and I want to inspect all the sites and all these sites are in between 1 or 2 kilometers in the railway compound only..So I am using a scooter to inspect these sites..Yesterday unfortunately I didn't use the helmet while going to the site from one another.On the way one police vehicle stopped in front of my vehicle and asked me to get down..I thought that they caught me for not wearing helmet..But the S.I asked me that why I didn't stop the vehicle when they asked me to stop before..Then I asked them that already I stoped the vehicle here then what's the problem.. But he said that he had shown his hand to stop my vehicle when the police vehicle was passing to the opposite side..I said that while I was driving I didn't see that the S.I tried to stop me before.He asked me to pay fine and I asked him the reason..His answer was too ugly and he compelled me to pay fine..I said to him that I am ready to pay the fine for not wearing helmet and I asked for the receipt.But the S.I was not ready to give me the receipt and he pushed me to enter into the police vehicle to take me to the police station..But I oppose them and inform the railway authority what had happed..Then the S.I informed the constable to bring me to the police station by my vehicle..But there was only one helmet in my scooter..The constable wore the helmet and he drove the scooter.But I haven't the helmet. When we reached at the station S.I filed the FIR and didn't give me back my vehicle. He filed the cases IPC 279 and MV act 132..how can I defend this wrong case