When Google finds duplicate pages, it can hurt your search ranking.

Unfortuneately, Google sees www and non-www pages as two different pages. So you will need a redirect so that only one address gets indexed.

In the .htaccess add the following lines

## ORGANICWEBS - rewrite www to non-www to fix canonical issues
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.mywebsite.com.au [NC]
RewriteRule ^(.*)$ https://mywebsite.com.au/$1 [L,R=301]

UPDATE...

## ORGANICWEBS - rewrite www to non-www to fix canonical issues
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ https://%1/$1 [R=301,L]