Nickname field isn’t appearing in Admin

When you display All Users, it will display values from users table. You will not see Nickname column, because Nickname value is in usermeta table. Put the following code to your child theme’s functions.php file. First filter manage_users_columns will add custom column Nickname to All Users view. Second filter manage_users_custom_column will retrieve values from usermeta table for Nickname column.

function wpse_add_to_user_table($column) {
    $column['nickname'] = 'Nickname';
    return $column;
}
add_filter('manage_users_columns', 'wpse_add_to_user_table');

function wpse_disply_in_user_table_row($value, $column_name, $user_id) {
    switch ($column_name) {
        case 'nickname' :
            return get_user_meta($user_id, 'nickname', true);
        default:
    }
    return $value;
}
add_filter('manage_users_custom_column', 'wpse_disply_in_user_table_row', 10, 3);

Please note that Nickname field is always present when you Edit user.