Can I reopen my case and fight it, even though I served time?

Question Details: I was at a washeteria and while standing outside, 2 under cover cope started searching people. One guy was caught with drugs, and then the cop said that I had drugs and I was arrested. I served time for this and I lost my green card. Can I reopen this case and try to get my green card back... The cops never found drugs on me, but I was scared and I did not have the money to fight the case, so I pleaded guilty Important Notice