The online form correction will very likely begin from 14 JANUARY 2019 upto 31 JANUARY 2019.

You cannot make changes regarding the self declaration in your application. 

Hi there.

The correction window will be open from January 19 to January 31, 2019. During the correction window candidates won't be able to change their category, gender, nationality, State eligibility and Pwd status but surely be able to change other details. 

Hence, application forms can be further edited only during the correction window. And, as you can see that you cannot change your Self-declaration now according to the strict guidelines being followed by the NTA I'd suggest you to call the authorities and ask them for clarifying the matter.

Hope this helps.