slight headache, drink some 100plus. or those drinks that is supposed to replenish your lost ions after an exercise. or place two thumbs at the beginning of your nose bridge, between the eyes and rub gently there for a few minutes.
neck ache, put warm towel around the neck region and rest in a comfortable position for 10 minutes.
blueblack, when you just knock into something and you suspect a blueblack to form, wrap ice cubes in hanky and apply on the knocked region for 15 minutes. if after one day, put warm towel on the region to make it go away faster.