I suggest cleaning out his nostrils the best you can. Get him to drink some cold, clean water. It might be best to do that with a syringe so he doesn't swallow what's on his beak. (If you do a syringe, be very cautious how you much you give him at once. If you give him a lot at a time, he could accidentally choke on it or it go down the wrong hole.) Offer him some moist mash too. (If you don't have mash, you can make some by throwing your pellets in a blender or smoothie cup.) If his feathers are all caked with that stuff, trim some of it out. If you're willing to try this, rubbing alcohol might help get some of that stuff off, but I'm not sure because I've never used it on something like that. (I use it to get spray paint off my hands, so that's why I'm thinking it might work.)
Can you get pictures of his leg? Because he was thrown out of a car, he could have road rash in a few places. Look for any raw skin anywhere, especially amongst his feathers just in case you've missed something. I would treat any open wounds with Hydrogen Peroxide for the first cleaning and a Saline rinse for the cleanings after that.
