@tanaythomas this "I have to use a flashlight" means it is your backlight that is not working. That could be a issue with the physical backlight on your LCD panel. It could also be that this is related to the backlight circuitry on your motherboard or the cable/connector from your motherboard to your LCD. Right now I would like to say that this "Can it be fixed without pulling up the laptop" would be a No. You will most likely have to disassemble your laptop and even take some measurements with a multimeter.