The OP asked about pain meds... you can give chickens aspirin ground up and sprinkled on their food. Just make sure they're not bleeding. You can also give them tramadol, but that's prescription.
Due to a demonic dachsund owned by a neighbor, I have dealt with multiple dog attacks. I try to always separate, and for me that means bringing it inside and keeping it in a plastic tub for observation, at least overnight. Put some hay or shavings in the bottom.
I also fashioned feed and water containers out of plastic cups, like sour cream, cottage cheese, etc. Make a u-shaped cutout, because you don't want them to be very deep, so leave them able to hold 1 1/2 to 2 inches food or water. In the back of the cup, pierce it with baling wire from one side to the next so that you can bend the wire to hang over the side of the tub. Make the wire fairly long, because you want to be able to adjust the height. A bird with a neck injury will eat more if it has to bend its neck less. If you need to picture it, it looks kind of like a swing chair. Birds who have pain in their neck won't bend it to eat as much as they need to, so feeder height is important.
If you have lost skin, neosporin works, but vetericyn is best, same for puncture wounds. It's pricey, though, and should be at your feedstore. You might find it for less online, but that won't help right now. If you go for neosporin, see if you can find a spray-on.
Feed extra protein, like mashed egg and yogurt. If you give antibiotics, they'll need yogurt afterward to rebalance their digestive health, and if they won't eat it, you can get probiotics at the feed store. Give them extra vitamins like a poultry drench from the feed store, or poly-vi-sol infant vitamins without iron from the pharmacy section at your grocery store.
I have some chickens who have had some pretty massive damage, and they're healthy, happy and productive today. If you have questions about specific injuries, give plenty of details and I'm sure somebody here can help.