to www or not to www

Hi, I have a conflict between the rss2_url and the posts_nav_link functions.
when I write this address as the blog address in the options: https://uriashi.com , then the posts_nav_link works, but the rss2_url doesn’t. however, when I change the blog address in the options to https://www.uriashi.com , then the rss2_url works fine but the posts_nav_link leads the visitor to a blank page.
my wordpress files are inside “blog” folder which seats in the root folder, and in the root folder I have an index file which redirects to the index file within the blog folder.