You can sue him in small claims court. If the claim is breach of contract you can get simple 9 percent interest per year (no compounding) otherwise no interest. You do not get attorney fees from him unless you have a contract that provides for that.
I am a former federal and State prosecutor and now handle criminal defense and personal injury/civil rights cases. Feel free to check out my web site and contact me at (212) 385-8015 or via email at Eric@RothsteinLawNY.com. The above answer is for informational purposes only and not meant as legal advice.