Apparently it can’t be uninstalled
As is the case with every new iOS version that has been introduced.
Next time, you might want to wait a few weeks and watch the support boards for potential problems before you take the plunge.
However, a Forced Restart can often solve a lot of issues, so it's worth a try if you have not already done so.
Follow the instructions very carefully, as this is a bit tricky. (Hint.....ignore the "slider" when it appears and keep holding the Side button in until the Apple logo appears. This might take another 30 seconds.)
Force restart iPhone - Apple Support
Good luck