Hacked index.php. Fixed, but now cant login to wp-admin

My index .php file was hacked and replaced with a ‘flashing lights with music you have been hacked’ page. I dleted it and replaced it with the proper index php file, but now i cant login to my dashboard. When i try it says ‘ERROR: Incorrect password. Lost your password?’ So i click on lost your password and enter my email address, and it then says “ERROR: There is no user registered with that email address.” What??
I have NO idea what to do, any help gratefully received.