You guys need to think more about the heads structure in your attempts at calculations and ponderings.

Different substances absorb force in different manners, as does structure diffuse. IE Skin and bone behave very differently under force. And then there are different strengths and weaknesses in the scull. Then an understanding of where nerves/blood vessels lay. Where the impact is will serve to antagonise/mitigate the blow.

If you have a hard tap to the right place on the head it is possible, as the flesh/skin would becomes inflamed and starts to heal, you may have a few burst blood vessels and if this is over a nerve the inflamation could cause the signals to get muddled for a few weeks (or much longer if the actual nerve is damaged, with greater force).