Dont worry, you have a chance to make corrections. All you have to do is email them about the error in your application and get t corrected. Go through point 7.1 of the brochure. It says

"7.1 Discrepancy and correction 

The candidate is expected to fill up all details correctly , check a preview of the application b efore submitting the same onli ne. Corrections will not be entertained, h owever in rare circumstances , in case corrections are needed , they will be addressed on a request by the candidate . Such requests may be emailed to nata2018helpdesk@gmail.com "

Go through the brochure from the below link

http://www.nata.in/NATA2018-Brochure.pdf