Preheat oven to 375 degrees.
Stir together egg, sour cream, milk, and oil in a bowl until combined. Add flour, sugar, powder, and salt. Mix until combined. Fold in peaches.
Spray a muffin pan with non-stick spray. Spoon the batter evenly into the muffin pan.
Place muffins in preheated oven and bake for 18-22 minutes, until muffins are lightly browned. Please note that the muffins tend to brown much more quickly on the bottom, so pay attention to avoid burning.