Default Phone works but backlight of the screen doesn't

Hello,

As you can see my issue is related to the screen... backlight always worked until some days ago where it failed somehow.
It started to fail when I flashed Stock Kitkat with the recovery but I don't think that it could be related...
My question is simple, did anyone faced this issue and resolved it?

My guess is that it has to be repaired but if there is a small chance it can be repaired from my side without opening it I'm willing to try it, otherwise it goes to reparation

[EDIT]
Apart from this issue the phone is working just fine, I mean it boots correctly, can enter in download/factory reset mode if I want too.
The only thing is if I adjust the brightness on the phone from Android nothing change, the phone is still dark and can hardly see what's in the screen.
[/EDIT]

Thanks in advance!