The the post id from image id

The featured image is stored as post meta with the key _thumbnail_id, so you could use a meta query to get posts with a specific thumbnail:

$posts = new WP_Query( array( 
    'meta_query' => array(
        array(
            'key'   => '_thumbnail_id',
            'value' => $attachment_id,
        ),
    ),
) );

Where $attachment_id is the ID of the image.