A bruise is a collection of blood cells that have gotten out of the blood vessels into the surrounding tissues. They must be broken down and absorbed. Putting vinegar on the surface of the skin does absolutely nothing.
Conkers. I remember playing this until all you had was a lump of white stuff on a string! I tried everything, baking them, soaking them in vinegar and all sorts to get them to last the longest! I'm sure health and safety has sadly now stopped this kind of great kids' fun in the playground!