I am unable to login into my wp-admin

You can fix this by changes site_url and home_url in your database.

If you have access to your database(phpmyadmin) go to options table and change site_url and home_url from HTTPS to HTTP.

You can also change it through wp-config file.

define('WP_HOME','http://www.example.com');
define('WP_SITEURL','http://www.example.com');

See: https://codex.wordpress.org/Changing_The_Site_URL for possible methods.
Hope this helps.