User Query – Meta Nickname

// WP_User_Query arguments
$args = array(
	'meta_query'     => array(
		array(
			'key'     => 'nickname',
			'value'   => '$new_nickname',
			'compare' => '=',
		),
	),
	'count_total'    => false,
	'fields'         => array( 'id', 'user_login' ),
);

// The User Query
$user_query = new WP_User_Query( $args );

// The User Loop
if ( ! empty( $user_query->results ) ) {
	foreach ( $user_query->results as $user ) {
		// do something
	}
} else {
	// no users found
}