+1 to Justin's suggestion. It is much more likely that some rear drive gear oil (the smell is usually distinctively different from any brake fluid, as well as color) leaked out from the top 'vent' cap (top of the final drive when the bike is standing on its wheels). It might also have leaked out through a seal or one of the inner cover bolts inside the wheel hub when the wheel is on. Either way, I'd take the wheel off, clean as Justin recommended, and check for obvious signs of continued leaking. IF you don't see anything, put it back together, and drain&refill the final drive with the proper amount of fresh gear oil. I'd also check the oil level in the swingarm, but I am a bit obsessive about maintaining lubricant levels.
If you actually got brake fluid on your rear wheel, it must have either come from the vehicle that hit your bike, or somehow your handlebars are wrapped around your rear wheel and it doesn't sound anywhere near that bad !!
