etc/sudoers.d: too many levels of includes-no valid sudoers source-error initializing audit plugin

I upgraded to version 22 over the internet. My sudoers file in /etc apparently has one too many lines of includes at the end of the file. Stupidly, I copied this file (sudoers) into /etc/sudoers.d. Hoping to edit the erroneous line, I now find myself locked out of sudo altogether. I get this:
sudo: etc/sudoers.d: too many levels of includes
sudo: no valid sudoers sources found
sudo: error initializing audit plugin sudoers_audit
Can you please explain how I must access and edit the sudoers file correctly?
Thanks.....
Greg