rear hub

[gazbenger]

i was taking my wheels off the other day, and noticed a chip out of my rear hub. They have gone a bit rusty. The chip is not on the outside of where you put the wheel onto though. How serious is this? and what should i do?
thanks

 

[pinky]

My drum looks like it has a "chip" in it...but thats just the way it is.
Sure it not just because its rusty and you cant see the definition.