You need to first use wp_get_post_terms() to get the term and then you can use that to get the term id to get the field from the category https://codex.wordpress.org/Function_Reference/wp_get_post_terms
$queried_object = get_queried_object();
$post_id = $queried_object->ID;
// now you can use this post id with wp_get_post_terms()
