If you have forgotten or your son has changed the code of your device, the thing you can do now is to recover the passcode in your email address (gmail), or you can do the hard reset to reset all the settings by default. steps below.
Here are 2 methods to make factory data reset on your phone:
Under power on mode Please go to menu-> “Settings”-> “Backup and reset”-> “Factory data reset” If you want to save data in the phone storage, please activate “Reserve the content of phone storage”. Then the data in your phone memory will not be erased after factory data reset.
Under power off mode Turn off the handset, press the volume up key and the Power key at the same time for a few seconds to enter the data format interface -> Select “wipe data/factory reset” via volume key -> Press “Power” key to confirm -> Select “Yes–delete all user data” -> Press “Power” key to confirm -> factory reset completed -> Please select “reboot system now” and press “Power” key to confirm to reboot your phone.
Please note that this method of user data format will erase all data from your phone (not include SD card files and current system software).