At that point in time it wouldn't be any different than just whitelisting your home or office IP address in your AWS security group. While such IP addresses do change, these days they don't usually change often and (presumably) you will know if they do. Therefore I'm not sure if you gain much by purchasing a VPN and whitelisting its IP address, unless your goal is to be able to connect easily when working at the local coffee shop.
Of course, limiting access via IP address hearkens back to the days of centralized networks, which are (hopefully) dying in exchange for zero-trust. So while this is (likely) a fine way to get started, this isn't necessarily as effective, easy-to-manage, or secure as a more robust access management system.
AWS in particular has the SSM agent that can allow you to connect to machines without having to open an external port, and you can also look into a PAM (Privileged Access Management) system. The former is something you could do now, while the later is something that is intended more for enterprises.
Which of these options works best for you just depends on your own personal risk tolerances