It's a bit perpelxing why you should have a field defect in only one eye - unless you have a previous eye problem.
It may be that the defect is spurious and does not reflect any genuine abnormality. The examining doctor should be able to work this out easily.
If it is due to a previous eye problem then its location and size will be important. Unless you can demonstrate no functional problems relating to this defect then it looks as if you may have a problem.