You should quit address book first. Then move the file to the desktop first. From the desktop you should be able to delete it from there.
Also, deleting that file won't delete the contacts. They reside in the metadata folder. That file you want to delete is just the database file. Also, if you are using iCloud, the information will actually lie within the Sources folder.
Why go through all that. Just select all contacts in the address book at once and hit delete. Then you can create new ones.