Here’s the code you can add to the end of your child themes functions.php file which will create a new widget that displays your content after all single posts assigned to a custom post type named portfolio.
If the name of your custom post type isn’t portfolio, you can change the name from portfolio to another in this line of code:
if( 'portfolio' == get_post_type() && is_single() && is_active_sidebar( 'portfolio-widget' ) ) {If your posts are simply assigned to a category and NOT a custom post type, then use this code.