MCI registration is for Indian Citizens who either are Indian Citizens who have studied MBBS abroad but are back to India and practise here or Indian Citizens who have studied MBBS in India. If you are a citizen of Nepal, you will not be eligible for MCI registration. Once you are married and move to India, you will have to reach out to the Embassy for the procedure of gaining Citizenship because you hold the virtue of getting married to an Indian Citizen and they will help you with the process. Then you can reach out to MCI for the next process.