sudo and su - both are not working as i have removed my local user from local group

I was trying to add my local user into www-data group but it was getting some issue so i have removed my local user from local group and add it to www-data group.

But now after restart system neither I am able to use sudo nor su -

Trying to use sudo :

"Sorry, user ronakchauhan is not allowed to execute '/usr/local/bin/apt update' as root on ronakchauhan"

Trying to use su -
"su: Authentication failure"

please help!