Small nick on edge of aluminum case.

I have worked with this issue many times. I have tried to work out the dent with a piece of hard wood and smack it from the inside. Remove all components in the way using the ifixit guides for your machine and use a piece of hard wood just larger than the damaged area so you don't end up with multiple dents on the other side. Using a rubber mallet strike the wood inside at the point of damage. * make sure the outside is against a large flat surface. The problem is to hit it with the right amount of pressure. In most cases it is wisest to leave it be and use it as a reminder to take it easier on your computer. If the damage is to the top radius the option is the same. But there is a greater chance to crack the case.

Hope this helps.

Also note, there is a chance of damaging the screen by hitting the case too hard