Why does my LED display black out at certain angles?

I went to use my MBP today and found that the display would only light when tilted at certain angles. I could still see the desktop logos when the screen was dark, so I know it must be an LED backlight/display problem as opposed to a logic board problem (...right?). Nothing's happened to the computer - no trauma, no water damage - since I used it last night; the only thing I can think of is that I did a little wood sanding, and some of the dust may have gotten into the display. Right now the computer's working fine, but only because I've got the screen at the proper angle and I'm afraid to move it for fear of further damaging the hardware. I'd go about using one of the many repair guides on this site to isolate the problem, but I don't know which guide to use because I don't know exactly what's wrong - from basic research over the past few minutes I know that a lot of screen-flickering is the result of worn out LCD inverter cables, but I know that can't be the problem, since this model has an LED, not an LCD, display. If not the inverter cable, what needs to be fixed/replaced to get my display back in working order? Thanks in advance for your help!