DB Error: Duplicate entry 'nkpd15u3d2jc4vldpk31l9oov3' for key 'sessions_pkey'

my website has this error""" DB Error: Duplicate entry ‘nkpd15u3d2jc4vldpk31l9oov3’ for key ‘sessions_pkey’ “”"""
i add this code to solve it in .htaccess “”" php_value session.auto_start 0; “”"""" but my website get this error after it.

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at webmaster@sjournals.com to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log.

how i have to solve it.