Focus on the "under-plane" (the nostrils and septum) rather than the bridge.
In the real world, there are no outlines—only where one shadow meets a lighter area. Secrets to Drawing Realistic Faces
The distance between the eyes is usually the width of one eye. The Five-Eye Rule: The head is typically five "eyes" wide. Focus on the "under-plane" (the nostrils and septum)
Ensure you have a true black and a bright white highlight. Secrets to Drawing Realistic Faces