<?php function custom_user_profile_fields($user){
$previous_value = '';
if( is_object($user) && isset($user->ID) ) {
    $teamleader_id = get_user_meta( $user->ID, 'teamleader_id', true );
}
?>
<h3>Extra profile information</h3>
<table class="form-table">
    <tr>
        <th><label for="teamleader_id">TeamLeader ID(required)</label></th>
        <td>
            <input type="number" class="regular-text" name="teamleader_id" value="<?php echo $teamleader_id; ?>" id="teamleader_id" required /><br />
            <span class="description">Type teamleader ID here</span>
        </td>
    </tr>
</table><?php }
add_action( 'show_user_profile', 'custom_user_profile_fields' );
add_action( 'edit_user_profile', 'custom_user_profile_fields' );
add_action( "user_new_form", "custom_user_profile_fields" );
function save_custom_user_profile_fields($user_id){

if(!current_user_can('manage_options'))
    return false;

if( isset($_POST['teamleader_id']) && $_POST['teamleader_id']!='' && is_numeric($_POST['teamleader_id']) ) {
    update_user_meta( $user_id, 'teamleader_id', sanitize_text_field( $_POST['teamleader_id'] ) );
} else {
    return false;
}
}
add_action('user_register', 'save_custom_user_profile_fields');
add_action( 'personal_options_update', 'save_custom_user_profile_fields' );
add_action( 'edit_user_profile_update', 'save_custom_user_profile_fields' );
function myplugin_check_fields( $errors ) {
    /*
    if ( $_POST['teamleader_id']!='' && is_numeric($_POST['teamleader_id']) ) {
        $errors->add( 'teamleadere_id_error', __( '<strong>ERROR</strong>: Invalid Teamleader ID.', 'my_textdomain' ) );
    }
    */
    $errors->add( 'empty_teamleader_id', __( '<strong>ERROR</strong>: Invalid Zip.', 'remmbravo' ) );
    return $errors;
}
add_filter( 'registration_errors', 'myplugin_check_fields', 10, 3 );