Display custom meta on page that has been check in custom post type

You just want a meta_query based on the current page’s ID:

$query = new WP_Query( 
  array(
    'post_type' => 'sidebar_boxes',
    'posts_per_page' => -1,
    'orderby' => 'menu_order', 
    'order' => 'ASC',
    'meta_query' => array(
      'key' => 'checkfieldBox',
      'value' => $post->ID,
    )
  ) 
);

You can really only depend upon $post in the way I did on “singular” pages and only if the the $post object hasn’t been altered by code on the page. If you have trouble you will need to use:

$post_obj = get_queried_object();
// now use $post_obj->ID instead of $post->ID