Help! i couldn’t login

originally i created the blog using this directory path: https://www.mydomain.com/blog. then i changed my configuration so that the blog folder is now a new subdomain (e.g., https://blog.mydomain.com). the folder still remains intact. i didn’t move it; just changed the config in my httpd file so that it points to the new subdomain.

however, i couldn’t log into the WP-admin. Please advise. i need to create a blog and i’m stuck.