Hiberfil.sys is the Hibernation file used to store the state of the PC when it last went into hibernation. If you delete it, it'll be ok, but will be created again on next hibernation. You could turn off hibernation though and it wont reappear.
For deletion of hiberfil.sys you should first go to
Start/settings/Control Pannel-Power Options
Then on page Hibernate uncheck the checkbox "Enable hibernate support" Otherwise the operating system will not allow deletion of the hiberfil.sys.