Not much you can do. Leave the judgment, as this will prevent them from getting any further debt in future for the next 10 years. Closer to the time, do the necessary and try to recover your debt. If they still do not pay, get another judgment, which will block them for another 10 years.
Forget debt collectors. It will cost you a lot of money and there is nothing they can do more than what you already did. Unless, you are referring to the 'bone breakers, who goes out and hurt them physically until they pay the debt. Problem is, if they do not have money, you can have them hurt as much as you want, you will still not get your money back and still have to pay those people who did the 'job' for you.
At the end of the day, write this off for now and consider it a lesson learnt.