I changed my UID, now I can't login. How do I fix this?

Use another Admin user to change it back.

If you don't have another admin user, try this: Restarting Setup Assistant to create Admi… - Apple Community

imageximage wrote:

Long story short, I mistakenly changed my UID from 501 to 1120. After losing all permissions to open settings, safari, and any other application, I reset my computer to try to remedy the issue. Now, I cannot login to my computer. I type in my password, and the computer stays on the loading page forever.

I tried to do "First Aid" on my system, but that didn't work. I've tried resetting my password in recovery, but that's not working.

How do I re-sync my User ID? How can I fix this issue?

See if there is anything here:

Changing your UID and GID - Apple Community

User account Advanced Options: shortcut to ****

Call Customer Support (800) MY–APPLE (800–692–7753)

or on line Apple Support