This happened to me when I was killed by a magma slime in the nether. When I respawned from my bed all I saw is this. I think my minecraft world is corrupted because this happens when I place torch on different places. Also this happened to me to another worlds. The light bug just stays permanent until you place lava or new torch. This can be annoying because it can be dark and you can't see anything. And it just makes your minecraft world looks weird.