Hard physical activity reduces sensitivity while caresses from gentle hands, or shower water, increases sensitivity.
I believe it’s all to do with the constriction or dilation of blood vessels. That is why athletes always warm up before strenuous activity to avoid muscle strain.
If the body is cold from the shower, it is more difficult for the body to increase blood flow to the area that has suffered the blow, increasing discomfort.
I think I have written before my belief that the rebound of a cane from the body contributes to the pain it causes. Could it be that on wet skin, the cane “sticks” momentarily, drawing the skin upwards with it as it leaves the surface?