Use Secure URLsin Admin Configuration
Yesthen my full admin panel has been changed.
If you are sure that the URL's are correct and you have SSL correctly set up then clearing your cache should fix this issue, as suggested by Renish K.R.
Since you can't clear the cache from Admin you will have to do this manually by deleting the contents of var/cache in the Magento root directory.
If you don't have SSL correctly set up, you will need to manually revert your change by editing the relevant values in core_config_data which is covered here: How do I fix my Base URLs so I can access my Magento site?