Broken world

My Minecraft world drops a message which says "the world has been corrupted. Please report it at bugs.mojang.com", it doesn't have mods, addons, skin packs, etc. I was playing normally just a few minutes ago (11:09 pm GMT 5) and it suddenly restarted and dropped that message, it is a big project which was a Realm for some time, it weighs around 235 mb, pls help.