Typically you will delete a file lock by deleting the local changeset as described in the section called “Tracking Developer Changes and Deleting File Locks”. However there are times where you only want to delete the lock for an individual file - not all the locks for the other files in the local changeset.
To delete an individual file lock go to the file in the version, feature or stream files. If the file is locked then it will appear with the lock symbol. Right-click the file and select 'Unlock'.