Noses are peculiar things...  & can be difficult to draw. Follow these steps to draw a realistic nose of your own...

Step 1: Draw an ellipse.

If you want to draw a realistic nose (or any realistic object, person, or scene), it is always a good idea to have a clear reference picture.

Step 2: Draw the shape of the inner nostril.

Step 3: Draw the shape of the outer nostril.

Step 4: Draw the bridge of the nose.

Step 5: Begin shading around the bridge of the nose and erase the ellipse.

Step 6: Add more shading.

Step 7: Darken the shadow within the nostril.

Step 8: Add more shadow.

Step 9: Final Step - Darken your shadow areas.