Check webserver logs, maybe there is no socket where PhpMyadmin trying to find it, you can create symlink, or modify phpmyadmin config and paste there correct path to mysql socket, or try to change connection method from "mysqli" to "mysql"
The exact command you'd use to check that can vary depending on which distribution you're using, but it might look like service mysql status or service mysqld status
If you can share the output of those commands, that would be a good start