A family of Microsoft word processing software products for creating web, email, and print documents.
Sorry to hear that you are having trouble with this. Being the only user does not necessarily prevent a file or its folder from having incorrect permissions. Does this happen with only this document or with other Word files too? Where is the document stored—OneDrive, Documents, an external drive, or another location?
As an initial test, copy the document to a new folder and try opening the copy.
Please also share a screenshot of the complete error.