You have two indentations. One feels like a bump between your ear and the back of your head, that is where the implant's magnet is located on your skull. Over time that bump will settle down and will not be noticeable.
The other indentation is right above or right behind your ear. That is where they drilled a hole in your skull to access the cochlea. It will always be there, and since the wire goes through that hole, every time you push on it you will feel a sensation inside your ear.
The magnet is about 3/8" diameter centered in a 1 inch diameter antenna. The inside part is nothing more than wires, and the magnet is only there to hold the external antenna in place.
The internal magnet is the opposite polarity of the external magnet, so the only way to make things stick to your head is to use a light duty refrigerator magnet. Be careful using those big ones, as you can yank the internal magnet loose if you have a strong enough magnetic field. Most everyday magnets are harmless. The worst you can do is get inside an MRI machine running at full power, it will do some serious damage.
Just be glad that the latest internal implant is much thinner than the older ones, my 2003 implant has a larger bump than my 2010 implant.