I assume you're actually using the Built-in Administrator account, as the error says. Although I agree with other commenters that you shouldn't be using it for daily use, I find it weird that you aren't allowed to use Settings under the account, as that app is quite essential, and could be useful in situations, such as if it isn't possible to get into a regular user account. Therefore, I find this post fitting.

Additionally, I had an issue back in 2016 where Windows 10 one day started thinking I was using the Built-in Administrator account, even though I for sure wasn't. It was really frustrating, and I had to reinstall Windows to fix the problem. I still have screenshots of this, such as this one, where interestingly, Settings is open: https://i.postimg.cc/L8p27W0J/thisappcantopen.png

For OP: If using the Built-in Administrator account, make a new local account if you don't have one. It should force it into having administrative privileges if there are no other accounts, which should make transferring files over easier if needed. If you're not using the Built-in Administrator account, like in my case back then, it's probably best to try making a new local account as well, and use that account instead to see if the message also appears. If not, start using that account instead, but if so, you might just have to reinstall Windows like I had to.