wordpress address

Hi Can anyone help?

I was playing around with the general settings and looking at the site address details as I was planning on doing some SEO and noticed that the pages were pointing to the folder on my host where I’ve developed the site. When the domain name is transferred I’ll make sure that the site address reflects this.

so the site has been developed and is hosted at
https://www.mydomain.co.uk/my-clients-site and https://www.my-clients-site.co.uk will be mapped to that folder when i have transferred it.

Trouble is, in playing around, I changed the site address in general settings from https://www.mydomain.co.uk/my-clients-site to https://www.my-clients-site.co.uk before the transfer has completed. and I can no longer log in as WP now thinks that the site is at https://www.my-clients-site.co.uk

Not sure what to do… when the domain transfers, will i be able to log in??

Appreciate ANY help
Thank you