There is an edit option even if you are filling the form as a January registered candidate.

For correcting this you have to register as a fresh candidate and must fill all the details correctly. NTA gives a chance for correction of details at the time of counselling process also, so if you haven't corrected it then you can correct it their also. But it will be safer if you register as a fresh candidate.

But if you register as a fresh candidate you will have to make sure that you secure more percentile then your previous Jee mains paper, because there will be no rule applicable to you for considering the maximum percentile in both of the papers.

I hope you got the point.

Good luck.