I logged into minecraft and noticed a huge hole/cave that looked like a bug next to my house, it was just like the other ones I attached images to. I tried to restart the game and the computer, but it didn't disappear. I patiently closed it thinking it was the only one, but then I went to my mine and came across a surprise with another big hole and another one further down. I'm not sure if there are more, but I am very disappointed and sad, because my mine is ruined and I'm not sure how I can keep playing in the world I had created because the holes are impossible to close without using cheats and it's very unfortunate. 

Is this fixable?