i had the same thing
I, too, had one of those from a couple rocks that flew off of a truck on the highway. Two hit the windshield and cracked it to the point of replacement while the third hit the side of the car just like yours.
While mine wasn't quite as large, it did take off the paint just like that. I opted for the temp and not exact fix which was to simply clean it and treat it with touch-up paint. Unless you are looking for it you won't even notice it, plus with all the freeway driving I do on a daily basis I figured that if I respray the whole door, Murphy almost guarantees that it would happen again within the week or some a-hole would get me in a parking lot regardless of how carefully you park.
I'm a huge proponent of keeping your car always looking in tip top condition but for me the price is too big to put all that money into something that you can't control from happening again.
Good luck either way you decide to go!
Jet Black 2012 BMW 135i E88 / M Sport Package / DCT / BMW PPK Stage 1 / Scopione Front Splitters and Rear Diffuser