Dear Vivek, the correction window was introduced to correct such errors in the application form. The reason your basic application form was acceoted was because AIIMS authorities don't know your personal details and take your answers as right information. Now that the correction window has been closed, you can do really nothing with the cirrection part. If this mistake is in regards to your Mother's surname, we would suggest you to leave it the way it is because some women after marriage take their husband's surname and their Maiden name can be still considered. Even if it is a smelling mistake, it should be ok. But if there is a total difference in the names, you may have to reach out to the helpdesk.