Police officers allowed hit while you are cuffed ?

Let me see if I can explain this issue: in 2003 my exwife and I were out on the town with another couple. To shorten the story I was in the back seat and her friend was driving with his wife in pgr seat. We left a bar, when driving home (yes the driver was intoxicated) He plowed into the back of a cop car and drove behind a building( stupid move) So now we have like 5 cop cars surrounding us. My ex wife and I immed get out and fall to the ground. All the cops are mad(with reason) Cops just kept yelling at us to "stay the F**** down. I am of course very drunk. But I see one officer drag my wifes female friend by the hair up from the ground. OMG. I then (drunk) stood up and said "hey you cant do that". When I did of coarse all the cops took me down. They cuffed me. I was so frustrated. Then frustrated...I put my head down, leaned forwardand a officer kneed my head and cut my ear. I now want to file charges. This was 2003. Is it to late to get a lawyer on this? Do I have a case still?