hi,

I hope you are asking about neet ug exam. yes you may correct it now, if you did not final submit the application form. if  you already submit it you may correct it when the correction window will open. correction window will open from 15 january, 2020 to 31, january, 2020.

follow the below link to know in details,

https://medicine.careers360.com/articles/neet

You haven't mentioned which exam are enquiring about. But if this is regarding NEET application, you will be able to change the details during the correction window. NTA will open the correction window from January 15th to January 31st. You can login and make the necessary changes. But if this is not regarding NEET, please do help us with the exam and we shall help you with relevant information.