I can't log in to my wp-admin. Help!!

how did you try to change the url of the login?

U need to go to your mysql admin tool, login and change the url back in the option tables.

On the ‘general’ tab in wordpress

Of course you can’t login because you’ve changed the domain name.
You can try this (this will be very technical):
Get inside your CPanel -> phpMyAdmin -> try to find this table “wp_options” (usually it’s located at left side of phpMyAdmin window) -> try to find “siteurl” inside column named “option_name” -> edit the value inside column named “option_value” by clicking the pencil icon. You must change the value with your first domain name (in this case “thesandwichdiaries.com/wordpress”). Once you edit the value you can save it by clicking the “Go” button.
Try to visit your site again (thesandwichdiaries.com/wordpress).

Hope this will help.

PS.
If you want to use only “thesandwichdiaries.com” as your domain then you need to reinstall WP in your root directory. OR you can move/migrate your WP from thesandwichdiaries.com/wordpress to thesandwichdiaries.com/wordpress

how do i reinstall wp in my root directory? or migrate it? sorry im not very techy!

Maybe it will be easier if you reinstall your site and not migrate it.

How to reinstall is just the same like what you did before when you installed your site on thesandwichdiaries.com/wordpress. Root directory means there’s no folder after it, (e.g root/wordpress), “wordpress” means a directory inside your root directory. I believe inside your File Manager there’s a directory called “wordpress”. So, you must leave empty the field after root directory.

If you want to migrate your site, you can use XCloner – Backup and Restore plugin.