iMac Cannot Log In

The password that i made for my administrator account doesnt work for some reason and i wrote it down i have tried typing it wrong and adding numbers and uppcase etc..i wanted to reset the password by holding "C" as the computer started and now it takes me to a log in screen where it ask for my password and i cannot log in because i dont have the password or the master password..also there are no other accounts and when i try holding the "C" button down at the begining it just goes straight to the log in screen so what do i do please reply..

Please don't double post.