Probably my thoughts deceiving me as usual. Though the blunt part of the knife hurt a bit and caused quite a loud sound, but it felt almost like the equivalent force of your hand knuckle bones knocking on your head, kind of the same sound occurs with both, just a bit more noisy with the knife probably due to the material and the fact that it's not covered in skin like the bones are. Regarding the pointy edge it caused quite an itchy feeling after, like as if my skin got pressed down and a small dot mark appears. But my guess is that the skin covering the skull is a bit more tough than that of ordinary skin? Maybe a bit like leather similar to that of the skin on the elbows?

EDIT:
When you mention: "concentrated energy" do you refer to the event of such a hard focused blow temporarily changing the shape of skull or fracturing it? I mean how's it possible that a hard blow to a small area can cause sub concussive impact if there is no movement of the head itself? If that's what you meant. Can the skull move even though the head doesn't when the energy is concentrated to a small area?