Code to add to your functions.php to only display Sticky posts on your main blog page

functions-snippet-sticky-posts-only.php

<?php

// add the following code to your functions.php file

add_action( 'pre_get_posts', 'fe_pre_get_posts_sticky_only' );
function fe_pre_get_posts_sticky_only( $query ) {
    if (
        $query->is_main_query()
        && $query->is_home()
    ) {
        $query->set( 'post__in', get_option('sticky_posts') );
    }
}