Sorry to hear about the scratch
Depending on the depth/width of the scratch (where is the pic of the scratch with some common currency next to it?! heh), you may be able to fix it with touch-up paint, or find someone that is good who can. Painting the whole panel is rarely necessary to cover a relatively small scratch like that, unless the impact that created the scratch also created a small dent (even then, sometimes a good paintless dent removal guy, ie DentMasters, can do a pretty good job removing the dent), or the scratch is really bigger than you're making it out to be.
My dad painted exotic cars professionally for years (that is until he found out all his clients were big shots in the mafia, thats a whole other story heh), and he can conceal some pretty nasty scratches with some simple touch-up paint or ideally with paint preserved from when the car was originally painted.
I'll tell you how he does it, but not without the obligatory disclaimer: do this at your own risk, I'm not responsible if you fudge it up, etc.
Start by cleaning the affected area - first by washing it as usual, then with wax and grease remover or by using a paintable pre-wax (this is so the touch-up will get a good grip on the surface, it doesn't stick too well to wax!). Using a tootpick - not the applicator brush that comes with the touch-up - apply a thin layer of paint to the scratch. If you can, do it in two thin coats instead of one thick coat (sometimes the paint is too thick to apply it this way though). After the paint has cured completely (read: wait at least two or three times as long as the label on the bottle says), wet-sand the area with ultra-fine 1200 grit sandpaper on a sanding block to flatten it out and make it flush with the rest of the paint. This takes some time, be patient! Feel the area you're working on regularly to gauge your progress. Professionals often rely their sense of touch more than their sense of sight with stuff like this. Be very careful of 'peaks' or 'high spots', as you can sand through the paint very easily in these places. Some people use 600 then 1200, but I've found it more difficult to polish it this way, and it's safer to just use the 1200 anyway.
Next cut it with a mild rubbing compound, then follow with your favorite polish and wax. He usually feathers out the area he cuts, or if necessary, rubs out the panel or whole car to make the level of shine match.
As an aside, I have found the quality of the paint on BMWs to be very high (though soft) with a negligable amount of orangepeel. If your car has more pronounced orangepeel, the area that you sand is going to be noticable (to the point where you will want to do the rest of the car!) as it will be perfectly flat and will look better than the rest of the car. DANGER: wet sanding is extremely contageous, you will want to wet-sand the rest of the car! But I would strongly discourage this... it takes practice to be good at it, and more importantly the process removes quite a bit paint. Usually cars that are going to be wet-sanded get a few extra coats to sand through so there will still be something left when the sanding is done.
If any of that makes you uncomfortable, I suggest you take it to someone who knows what they're doing. If you're feeling ambitious but you haven't had much experience with this sort of stuff, it would be best if you practiced somewhere less conspicious first. The rocker panels are usually a good place to look for a small chip. Try your hand at repairing something small like that first before going on to the big noticable scrape. Or better yet, practice on someone else's car who doesn't really care what happens!
It actually sounds as though you may be able to simply rub it out with some polish or mild rubbing compound if it isn't that deep. Without seeing it, it's really hard to tell.
Hope you find something useful in all that. Come to think of it, I hope you can make sense out of it at all; I'm far too tired to be writing stuff like this at this hour! heh
Good luck...
--SONET