A child support lien, in most States, has to be repaid out of injury settlement proceeds from a tort claim. In most jurisdictions, an attorney is required to notify the agency which enforces child support payments, such a Department of Revenue, about a third party liability claim (i.e. such as a car accident case), so that that agency may place a lien on the case for repayment.
The bottom line is the answer does depend on your State's law; however, do not be surprised if the child support amount in arrears has to be paid before you receive your net settlement check. Check your State's law. If you have not told your attorney about this issue or he/she is not aware of it, then you need to make full disclosure. Depending on your State's law, you could be severely penalized or sanctioned for noncompliance.