how can i sue a contractor that owes me money from a settlement

That depends upon the language of the settlement agreement. Does it entitle you to enter a judgment? Was a confession of judgment signed together with the settlement agreement?  If the answer is "yes" to either of those, you enter the judgment and proceed with collection. If not, you start an action for breach of settlement agreement by making a motion for summary judgment for an account stated. After the motion is granted, enter the judgment, and collect it.