Looks fine to me... Just clean it down with a soapy cloth to get the organics off of it and then let it dry out. The dark colored part is a good thing since that's a layer of aluminum oxide. You WANT that in the pot, since it's a naturally occurring, VERY HARD barrier between your wort and the aluminum. Generally speaking, pots used to brew in are that color (or even darker) inside. You want that wherever wort will touch, to have that barrier.
Do NOT use harsh/abrasive cleaners to remove it.