To be blunt, stop trying to find an answer on the internet and get him to a vet NOW! He should have been seen at an emergency vet last night, in truth, but you need to just bundle him into the car and go. Now. Please let us know how he is when you get home.
Ghilly
He needs to see a vet ASAP!! There could be swelling in his head causing damage. I would be very concerned about the blood. My pup has fallen several times really hard and never had blood.
You didn't say how big he is (breed), but at 8 weeks he shouldn't be too big to handle/transport. You may need a big laundry basket or some other means of lifting and moving that doesn't require continual handling of his body.
I have no idea what kind of stairs he fell down, but I would think a small dog would not break bones from rolling down stairs, I assume he wasn't dropped from someones arms while on stairs, that extra height could be serious.
We had a puppy that fell off our deck, one story off the ground, so like a flight of stairs in one step. He broke a front leg, but was otherwise fine.
Yes, he was taken to the vet and his leg set and splinted.