In setting up nginx and php-fpm I uninstalled Apache (httpd) and in turn that uninstalled the standard php package that Apache uses.
In doing so this deleted some files in the /var/lib/php folder including the session folder (/var/lib/php/session). While logging into phpmyadmin it threw an error complaining about the missing folder.
It's a simple fix, replace the session folder, making sure that the php-fpm process can read and write to it.
I had changed the user php-fpm runs as from apache to nginx to match the nginx user. This can be done in the /etc/php-fpm.d/www.conf
file.
Once that's done I ran the following to make it writable/readable by the nginx user.
# cd /var/lib/php # mkdir session # chown root:nginx session/ # chmod 770 session/