NextJS and Vercel CNAME for www domain

I have finished my web page in NextJS, pushed to GitHub and from there deployed the project via Vercel. I have set up custom domain DNS - added the required A record - and set in Vercel to use this domain. Everything works well, just a small thing going wrong. Whenever I try to access my domain like this example.com or https://example.com there are no issues, only problem appears when I try to access it like www.example.com - with the "www".

What would be the solution for this? When using ReactJS with GitHub pages I had to add CNAME into my domain DNS settings, do I have to do something similar now?

Thank you.