World went blank, then respawned to a giant hole

When I opened the world I have been working on for the past month, the world first opened up to black. Usually it loads after a while, but this time it didn't load at all. Since had cheats on anyway, I tried teleporting, then going high to kill myself, and eventually I just used the "/kill" command to sepuku my character. When I respawned, the world was back except for a giant hole where I had just been. The hole goes all the way up and down, and it won't let me enter that area. I also tried accessing the area through the top and it won't let me.