As background, a "statute of limitations" is a law that imposes a strict time limit on your right to file a lawsuit against a defendant -- meaning against a doctor or health care facility, in the context of a medical malpractice case. If the deadline has passed and you try to file the case anyway, it's a safe bet that the defendant will ask the court to dismiss the case, and that the court will grant that request. That's why it's crucial to pay attention to the statute of limitations as it applies to your case, otherwise you'll almost certainly lose your right to any civil remedy over the alleged malpractice.
You can find North Carolina's statute of limitations for medical malpractice cases at North Carolina General Statutes section 1-15. This law (along with section 1-17) sets time limits for a number of different scenarios.
While the specifics of the filing deadline can be a bit confusing -- especially as to when the "clock" starts running for purposes of the rule -- the statute makes clear that you have at least three years to file the lawsuit after the occurrence of the underlying medical error.
But if the injury is not readily apparent at the time the medical error happened, and is not reasonably discovered by the patient until two or more years have passed, then the patient has one year from the date of the discovery to get a lawsuit filed against the health care provider.
Finally, section 1-15 mandates that no medical malpractice lawsuit can be filed in North Carolina if more than four years have passed since the commission of the medical error, except for cases where a foreign object (such as a surgical instrument or a fragment of a sponge) is left inside a patient. In those situations, the lawsuit must be filed within one year of the date on which the foreign object's presence is discovered, provided that the case is filed within ten years of the date on which the underlying surgery error or other mistake was made.