Do not place these elements on different layers, because it will be difficult to connect them to the rest of the skin on the face.
Step 2. Let's start. Illuminate mid-nose from the top to the place where it will be the nose tip. Shade the skin around the wings and under them as well as on the sides of the nose. Depending on the direction of the light obscure one side of the nose more than the other. Area under the nose tip (between the nostrils, but above them) must blur also. Illuminate the edges of the nostrils (this is not logical, but gives a more accurate form of nose). Also you can start to obscure the skin under the nose. All the operations above should be performed by using burn and dodge tools.
Step 3. Final. Increase the shadows level over processed areas, especially around the nose wings. Illuminate the tip of the nose. According to its type you can make even a bright reflection. If there is a flat nose, then you should not illuminate a lot. If it is large nose then you should do a flare bigger. Make a shadows on the rest of the skin around the nose. Imagine the approximate location of the eyes and mouth.Note: It is not a complete tutorial with the tools list and step-by-step instructions. But I can say that you can get such a results using just burn tool and dodge tool. And remember: practice makes perfect :) Fell free to ask questions and leave comments.