Past credit habits can impact your credit score negatively. This can happen, and that is why we always encourage members to get a written document to memorialize the account being closed, and also pull a annual copy of your credit report so that you can be alerted to anything funky sooner.
Bad credit history can take several months or years to improve.
The only thing to do now is to negotiate a payment arrangement and get that balance paid off as soon as you can. The creditor may be willing to waive some of the fees and charges, so I would be sure to ask for that.