Mistakenly changing the blog address: now unable to log in

Hi everyone.

I successfully installed wp a few hours ago. I have the file in a subdirectory (https://www.lewisheriz.com/mighty/blog), which has a web address (www.mightymighty.co.uk) pointing to it. In one of the admin tabs I changed the address to be shown in the bar to the one that corresponds to the address pointing to the directory (www.mightymighty.co.uk/blog). I didn’t need to do this as it worked with that address anyway…

Immediately, I was taken to a simple login page, and when I now try to log in, it just refreshes. Neither addresses work because they’re forced to point to a non-existent subdirectory.

How can I remedy this?

I’m completely new to blogging so do excuse me for my ignorance!

Thanks
Lewis