How do I amend my NC state return? It has already been accepted.

NC does not tax military retirement income. The TurboTax "Review" kept telling me it found an "error" in my filing because I entered the amount of my military retirement income. It said this was an error. So I entered zero. And my $127 refund went to a multi-thousand dollar amount I allegedly owe the state. I should not have listened to the TurboTax "error" popup.