I was trying to add an image like a “new” image to the posts which are just published and are less than 2 days old.

I tried using a function like this within a WP_Query but it is applying to all posts.

add_action('the_title', 'insiderable_add_img_new');
function insiderable_add_img_new($title) {
    $title = '<img src="http://insiderable.com/wp-content/uploads/2020/03/newicon.gif">'.$title;
    return $title;
}

This is what I tried with WP_Query:

$events_query = new WP_Query(array('post_type'=>'post', 'post_status'=>'publish', 'posts_per_page'=>-1)); 
if($events_query->have_posts()) : 
    while($events_query->have_posts()) : 
       $events_query->the_post();
       if (get_the_date( 'Y-m-d' ) === date( 'Y-m-d' )) {
        add_filter('the_title', 'insiderable_add_img_new');
    }
endwhile; else: endif;
wp_reset_postdata();
function insiderable_add_img_new($title) {
    $title = '<img src="http://insiderable.com/wp-content/uploads/2020/03/newicon.gif">'.$title;
    return $title;
}