Almost certainly they can sue you. You borrowed money from them online, and when you did so, almost certainly you agreed to a set of contractual terms which included the obligation to pay them back. If you haven't paid them back, you've breached the contract. Probably the contract requires you to pay their reasonable attorney's fees incurred if they sue you. And almost certainly the contract specifies that the court has to apply the law of THEIR state when it decides the claim. So poke around and see if you can find the contractual terms to which you agreed when you borrowed the money. Chances are the earlier you pay, the less you'll have to pay.
Not legal advice as I don't practice law in North Carolina. It's just my analysis of the facts you present in light of general principles of law. If you need legal advice, please consult a lawyer who holds North Carolina licensure.