Hi, I am privileged to help you get more understanding about your current concern.
Because you delayed you period by taking the hormone norethisterone (NE), it may take another full menstrual cycle for your period to return to normal. The effect of NE on the menstrual cycle varies with each individual based on how quickly the hormone is absorbed or broken down in the body and the dose of the hormone taken. As a result it will be difficult to predict exactly what day your next period will start. Since your period was occurred 12 days later than normal you should expect your next period to be at least 8-12 days later than when it would have normally appeared.
Let me know if you have any further questions regarding this question as my goal is to make sure you are completely satisfied with your answer.