Police refusing to file an F.I.R against a copy and others

Hi all, My name is Rakesh, and i live in mumbai where im persuing law. I would like to get some help from you all. Well on the 31st of December, 2015 a guy from the Mumbai Police along with other six were in our building premises and were drinking alcohol while making a lot of noise while playing music. I was asked to join them by the one who I know. Well i did join them but I didnt drink coz I already drank a beer earlier with my family. Some time later on really pity issues the guy from police started abusing me which I objected but he got more furious and punched my face which broke my two teeth with lots of bruises on my body. Soon all the other six too joined to beat me. I somehow recued and approached the cops. Now 1. The cops never filed an FIR. 2. They took me for medical but I didnt got any medical assistance instead I was forced to put my thumb impression on a medical paper. 3. Insted of filing an FIR they charged Me and Two others with 1250 rupees and my charge was paid by the guy from the police who assaulted me. 4. I approached the Asst. Comm. of Police who directed the senior police to investigate the matter but the senior cops and other seem to be protecting the accused cop. 5. I was not even given the copy of medical report and hence two one day later i approached a different govt. hospital to get the detailed med report coz the earlier hospital refused to give me a copy by saying that i can collect it from the cops only. 6. I recorded audio converstaion of the accused in the police station where he was admitting that he has beaten me... Now can any one tell me what should i do next? Should I file a private case in court? If yes then can u people guide me on what all options do I have... Also please let me know under what sections I can file a private case on them... Plz help me to go ahead... Thank you all in advance