Preheat oven to 210°C. Sift flour, salt, baking powder and nutmeg into a small bowl.
Stir together sweet potato, oil, milk, egg and sugar in a medium bowl. Stir in flour mixture just until evenly moistened.
Turn dough out onto a floured work surface. Pat out to a 2 cm-thick round. Cut into rounds with a 6 cm biscuit cutter. Place rounds on a baking tray about 2.5 cm apart. Gather up remaining dough. Pat into a circle; cut out remaining scones.