Save the document in a different file format. If you can open the document with your version of Word, saving it in a format such as .rtf (rich-text format) or .txt (ASCII text format) may strip out whatever codes corrupted the file in .doc or .docx format. After opening the converted document, you can then re-save a new version of the document in .doc or .docx format to see if the problem returns.
Be aware that .txt format does not support text-formatting features such as bold, italics, and underline. If your document featured extensive formatting, save it in .rtf format to preserve the formatting before re-saving it in .doc or .docx format.
Note also that some Word documents may be corrupted in such a way that a file saved in a different file format in Word may not be able to be opened again.