The only way to collect a debt like this is by filing a lawsuit. In Ohio, you would file in Municipal Court. In Pennsylvania, you would file in District Court. The state where you file depends on where the contract was made. You can act as your own attorney but it is always more advisable to retain an attorney.
If you win your lawsuit, you then get a "judgment" which allows you to collect. If he does not pay the judgment, you may be able to place a lien against any real estate he owns.
If there was no written contract, the lawsuit may come down to he said vs. she said -- a tough thing to prove. Loans -- even to loved ones -- should always be done in writing.
NOTE: Any information contained herein is intended for informational purposes only and should not be construed as legal advice. Always confer with a qualified attorney in your state who can review the individual facts in your specific case.