What can I do about a wrongful civil judgement against me

In May of 2012 I opened a credit account for my masonry company and in order to do so i signed a demand judgement note for $5000.00 - we were approved for the account and never even used it because we paid cash for the materials and I just found out that on my credit report there is a civil judgement against me in the amount of $5000.00 - it is a derogatory public record & is absolutely incorrect because we do not owe any money at all. I was wondering why all this time our credit scores were harmed and we couldn't refinance, etc. - for over 1-1/2 years. What can I do to rectify this situation immediately? Please advise. Thank you