I'm sorry to hear that you're having issues with the eraser function on your Apple Pencil since updating to iOS 16.1. It's possible that this could be a bug in the software, and it's worth checking to see if there are any updates available that might address the issue.
To check for updates on your iPad, go to the Settings app, tap "General," and then tap "Software Update." If there is an update available, download and install it and see if that resolves the issue with the eraser function on your Apple Pencil.
If there are no updates available or if updating the software doesn't help, you may want to try restarting your iPad to see if that resolves the issue. To restart your iPad, press and hold the power button until you see the "slide to power off" slider. Then, slide the power off slider to the right to turn off your iPad. Once your iPad is off, press and hold the power button again to turn it back on.
If you're still having issues with the eraser function after trying these steps, you may want to consider contacting Apple Support for further assistance. They may be able to help troubleshoot the issue and provide additional guidance.
I hope this helps resolve the issue you're experiencing with your Apple Pencil. If you have any other questions, please don't hesitate to ask.