Black screen when booting into Mac , external monitor works
I know this may sound bizarre but have you checked your native screens settings? Such as brightness controls etc?
If they are all correct, have you tried running the MBP with power plugged in and the battery removed?
Otherwise, have you tried re-seating the ribbon connector for the screen? You can find the guide here: https://www.ifixit.com/Guide/MacBook+Pro+17-Inch+Unibody+Display+Replacement/3438 
However, if this is a mid 2016 model, then I wouldn't hesitate to go the warranty route with apple and opening it up could invalidate your warranty.