Hello there!
Relax!
Such glitches are meant to happen specially during such times when everything is online.
Check your 12th marksheet as what that will be considered for the rest of the document filling procedure.
If there is a error there too, then try to contact the authorities for making the correction. It might look like a tedious task but it is not.
Drop a mail to the examination board and get your correction done.
In case of other board, it is generally done by a legal way.
Kindly get in touch with your school authorities for the same in order to avoid further troubles.
Good Luck!