dont delete anything yet.. first ensure ur aadhar DOB is fully updated and processed and u have the updated aadhar in hand.. inform abt ur aadhar DOB correction to the school or board officer whoever issued ur apaar id and ask if they can regenerate the appar id using aadhar details.. if not then check the official website of the board ask them if their system allows api sync with aadhar update.. have alternate proof ready such as birth certificate, school marksheet etc.. apply for exam only after this mismatch is fixed