Q: I changed my Apple ID to my current email and I cannot log on to my Mac mini

You could try & change the Apple ID back to what it was before.

Then, see about how to correctly change the computer ID or the

user account info, properly, once you can use the Mac again.

There is a correct way to change these things; it would appear

you may have mistakenly done something it doesn't like.

Good luck!

Note: If you've activated FileVault, this procedure doesn't apply. Follow instead the instructions on this page, under the heading "If you forget your password."

Start up in Recovery mode. When the OS X Utilities window appears, select

          Utilities ▹ Terminal

from the menu bar at the top of the screen—not from any of the items in the OS X Utilities window.

In the window that opens, type this:

resetp

Press the tab key. The partial command you typed will automatically be completed to this:

resetpassword

Press return. A Reset Password window opens. Close the Terminal window to get it out of the way.

Select the startup volume ("Macintosh HD," unless you gave it a different name) if not already selected. You won't be able to do this if FileVault is active.

Select your username from the menu labeled Select the user account if not already selected.

Follow the prompts to reset the password. It's safest to choose a password that includes only the characters a-z, A-Z, and 0-9.

Select

           ▹ Restart

from the menu bar.

You should now be able to log in with the new password, but the Keychain will be reset (empty.) If you've forgotten the Keychain password (which is ordinarily the same as the login password), there's no way to recover it.