Thanks for your post.
To delete the Nickname field, pull down the File menu and select "Manage -> Database...". Click on the Fields tab and you may see the Nickname field listed there. If so, you can delete it.
If the field is not there, click on the Relationships tab, and you should see a graphical representation of all the tables in your database file. You may have one table that is dark gray in color saying "Table Missing". Delete this table and you should then be fine. Return to Layout Mode to remove any field heading.
If you want a Nickname field to appear on the layout, add it to your field definitions.
If you need clarification for any of the above steps, please let me know.
I have a different problem. My table shows up in the Relationships window and in the Tables window (where it shows 1 field with 30 records) but when I open it in Table View or Form View, no data appears & I get a message that the table is missing. When I try to re-import the data, I am not allowed to choose that table to import into. What's up?