If the world is so important to you, why did you use it in beta? And if you wanted to use it in beta, why didn't you make a backup? Wait for beta to release, you might be able to play your world again.
You should read what the "Xbox Insider Hub" says before using any of their betas. If you open a world up in beta, you can't use that world again when you stop using the beta, so Like Tails1 said, make a copy of the world if you want to use your world in the beta.