the best way to understand skin is to find a picture on the net, and open it in a paint or photo shop program...take the eye dropper and venture through the colours and tones on the face
right now you need more shadow before anything, the face is flat except for the highlights
the brow (his left) should slowly darken as it comes towards the nose, and the other brow should be the same tone as that darkness..this will emphasize the lighting on the left side of his face
for highlights in shadowy areas, desaturate your colours..so for example the cheek on the left, if you desaturate it, you can maintain contrast and depth while showing its a shadow
if im wrong on the directional lighting goal...then ignore it, and ignore this part as well....right now the left side of his face is flat and too dark for light coming in that direction(even a soft angle from above to the left) you will find the first things i mentioned about the lighting and highlights will help you with the side of the face as you wont have to brighten as much
the spot under the cheek will also be slightly darker, while the spot close to the nose slightly brighter, this empahsizes the natural curves of the face
its looking good though
Starks