Because most blacklist issues resolve themselves when you stop the problematic sending behavior there is a good chance that the issue with the blacklist has been resolved already.
Because you don't want your mail to be blocked moving forward you need to make sure you address the problem moving forward. If you don't you could damage your delivery rates to a greater degree.
For steps on identifying the problematic sending behavior and preventing blacklist issues please see our blacklist remediation article.
For additional reference - Blacklist Deep Dive