Paths don’t match…

Google is telling me this:

We’ve detected that you submitted your Sitemap using a URL path that includes the www prefix (for instance, https://www.example.com/sitemap.xml). However, the URLs listed inside your Sitemap don’t use the www prefix (for instance, https://example.com/myfile.htm).

Can anyone help me understand what I can change in order for my sitemap.xml file to contain urls with the www. prefix?

Thanks!