I cannot login using my admin after bailing out of Tech Tool 10. I created another admin login using guest login on my 2012 mac mini, but cannot login with my original admin.

I made a protogo file on a flash drive and ran all sorts of tests on my internal 1TB SSD, which I'm using as my boot disk and on my internal Mac 1TB HD. Nothing shows up as a problem on either one. What do you recommend that I do next? I've been thinking about something which may work, which I shutter to actually do: remove the 1 TB SSD from my mac mini, place it in a 3.0 USB external sled enclosure, then reformat the SSD and then migrate my files from the mac HD, which is a 5400 rpm platter. However, if I can avoid this procedure because there's another way to get into my original user admin login, I'm all for that.

Any recommendations?
Regards,
Dennis Evans

I do not know what you mean by "bailing out of TechTool 10", or what you think caused the original administrative account to no longer work. The tests in TechTool Pro are read-only; only the tools make changes to the disk.

Check to make sure you are using the correct password for the administrative account. I had not logged in to one of my accounts for such a long time that when I tried to do so, I mistakenly used the corresponding password for its Apple ID.

You should be able to boot from the Recovery HD volume, reinstall the system software, and then migrate your user accounts, applications, and user files from a Time Machine backup, or a bootable clone of your usual startup volume.

The relevant Apple Support document:

About macOS Recovery.