Word automatically saves copies of the documents you have opened in a specific path set up by default. The path can be accessed form the Office logo > Word Options > Save. It should be something like:
C:\Users\USERNAME\AppData\Roaming\Microsoft\Word\. Access the location then try to open a previously saved version of the document. Alternatively, try opening the file in another computer because you'll be surprised to find out that the error may be caused by your Word installation.