@broanl I wouldn't sand even with the finest paper. The original surface of the leather leather won't match the sanded spots. They will stand out, take dyes and finishes differently, usually darker.
You could try with a Sharpy felt tip pen to darken just the spots.
Another possible is to use a cotton q-tip with deglazer or acetone to remove the finish and the glue or contaminant, carefully re-dye just the cleaned spot and apply the finish. You may be able to blend the dye and finish into the surrounding area as you apply it.