Add custom widget to WordPress dashboard

dashboard-custom-widget.php

<?php
add_action( 'wp_dashboard_setup', 'my_custom_dashboard' );
  
function my_custom_dashboard() {
global $wp_meta_boxes;
 
wp_add_dashboard_widget( 'mycustomwidget', 'My Custom Widget', 'display_mycustomwidget' );
}
 
function display_mycustomwidget() {
	if( isset( $_POST['mycustomwidget_nonce'] ) ){
		if( wp_verify_nonce( $_POST['mycustomwidget_nonce'], 'mycustomwidget_action' ) || check_admin_referer( 'mycustomwidget_action', 'mycustomwidget_nonce' ) ){
	        update_option( "my_text", sanitize_text_field( $_POST["my_text"] ) );
	    }
	}
?>
<form method="post">
	Hello Dear!
	<input type="text" name="my_text" id="my_text" placeholder="Enter the text" value="<?php echo esc_html( get_option('my_text') ); ?>" />
	<input type="submit" name="save_my_text" id="save_my_text" class="button primary-button" value="Save it" />
	<?php wp_nonce_field( 'mycustomwidget_action', 'mycustomwidget_nonce'); ?>
</form>
<?php
}