The camera of my nokia

You will need to format your phone and restore it to factory settings. Backup your data before you start the format. To format:
Press *#7780# on your phone, it shall ask you weather you want to restore the phone to factory defaults? Select Yes, enter the security code (default is 12345) the phone shall restart. Now once it comes back, press *#7370# and follow the same process again. After it comes back, everything should be working fine.

In case you do not remember the security code, then turn off the phone, press the star key (*), number 3 key and Green keys (the one used to make the calls) together and keeping them pressed turn on the phone, do not release the keys until you see the formatting screen, let it complete and the phone shall restart and then it should be working fine.