Thank you for your reply!

My mom called some vets who referred us to an actual avian vet, and they said the office visit would be around $125, not even including what he would need done (something about putting a cone on him)

I did some more research and found that pulling the feather out was also a bad idea because we might pull it the wrong way, and it's not all that common to pull them out. This is the website I found it on: https://birdsupplies.com/blogs/news/...-blood-feather

My brother and mom looked at Domino, and we all agreed that the blood looked very dry, and he wasn't bleeding so we didn't take him to the vet. (I also couldn't get him in a cage to take him, and I think I hurt his feelings chasing him around and trying to put him in one...I think he forgave me, though, because he was back on my shoulder pretty soon yesterday)

I stayed with him all day yesterday and he acted normal. Today, I come in and the tail looks a lot better. I can barely see any blood, and he acts as if nothing's wrong. I know birds act like they're fine when they're sick or hurt, but I'm very sure he's okay.
He didn't peck or preen his tail yesterday, either. He'd preen in other places, but not the tail.

I'll keep an eye on him, and if anything else happens, we can call the vet again.