This will allow the wound to heal without detracting from the look of your Bonsai. Protect the area with some grafting compound because bark will not grow over these areas for quite a few years. If you take the extra time to treat these wounds, they will be undetectable after they heal. Actually, after you have the desired shape after its initial pruning, you shouldn't do it again. Nipping maintains the shape of your Bonsai.
Some folks refer to it as pinching back.
They are the same thing. You nip your Bonsai to control new growth so that your mini-tree doesn't become so dense that it has to be pruned again. When you nip, or pinch off buds on a branch, it allows of side shoots to grow, giving your Bonsai a thicker appearance. Nipping also helps to grow better foliage. When new growth tips appear, nip them with your fingers by twisting them.