Take the sonuffa bitch to small claims court. You don't need a lawyer in Small claims court, but it would be VERY GOOD if you can prove the loan with a piece of paper, say, an IOU, or a check which he cashed and signed. An eyewitness would be good too, but beware of trying to get witnesses to court (ALWAYS subpoena a witness, even if... no make that ESPECIALLY IF the witness is your own mother).
I'm a lawyer and I'll tell you one thing that will result from your suing him. Win or lose, you will start to respect yourself and start to feel like you're a person who won't let others walk all over you. Look, even if the guy is truly judgment proof, you'll probably win the case and still not be able to collect, but WHAT THE HELL!!! No better fun than giving a shithead his "due" in court. NOTE - most jurisdictions have a ONE YEAR statute of limitations on ORAL agreements - meaning if you didn't get anything signed, then you gotta sue him in one year or FORGET IT. I don't know where you live or what your "transaction" looked like, but check the law, it's very easy to do. Call a lawyer and ask for ten minutes of advice - most lawyers will give it freely. NOLO PRESS makes a great book for California (and another one for all 50 states): Everybody's Guide to Small Claims Court. This book will walk you through it. SO STOP YER SOBBIN' and GO GETTUM TIGER!!!!
P.S. Let him call you selfish and try to slam you. Whenever you hear it, simply say tell everyone the true facts, and point out clearly that HE is the one who was not only selfish BASTARD but also dishonest, and instead of paying you back, he FORCED you to sue him. The truth is a complete defense to slander.