You can unlock the account by using the command prompt -
Step 1
Login to your account -
sqlplus "/ as sysdba"
OR
sqlplus $username/$password
Run any of the above two commands. If you run first command, then it might require your username and password. In second command replace $username and $password with actual credentials of database.
Step 2
After login execute the following command:
alter user $username account unlock;