Admin locked out after domain mapping

I’m locked out of my own subsite I created after mapping the domain.

It doesn’t matter trying all my logins including administrator.

When I click lost password it takes me back to the main site, I reset password, try to login to the subsite and still no access.

I’ve looked in phpmyadmin but I don’t know whether I should delete the mapping from there as I can’t get into the subsite to remove the domain mapping.

Can anyone help here please…