Hi
If you have forgotten your Restrictions passcode, then you will need to erase your iPhone and then set it up as new in order to remove or change the Restrictions passcode.
If you have a backup of your iPhone that was made before Restrictions was turned on, you may then wish to restore it from that backup. (Restoring from a backup that was made when Restrictions was turned on would only restore the restrictions with the same passcode again).
More information and instructions: