Chosen Solution
I dropped my phone yesterday and after putting it together I notice the backlight doesn’t work… how can I see if its a minor problem???
dhaslem8 “dropped my phone yesterday” would make it most likely a broken LCD backlight. Replace the display for a repair. Use these guides to work on your phone. Yes, there is always a chance that just a ribbon cable (unlikely) came off, or that the logic board (hopefully not) got damaged, but I’d suggest you start with the display.