Of course the best course of action is to take your budgie to the avian vet asap. The chance of infection is high with cat saliva or claws. Did you at least wash the area with water right after it happened to flush it out? Sterile saline would have been the best for an immediate wash. At this point you can try it, but again..
nothing beats a vet visit since there is a real chance of infection after injury from a cat. If you’re able to borrow money, that would be great.
It’s a good idea, even necessary, for everyone to set up an emergency fund for your animals. All the more so because you do rescue, and you never know the health history of the animals.
I’m sure you’ve learned after this (albeit the hard way) to make
extra sure from now on that your predatory and prey animals are securely separated.
If you haven’t already, please read the Stickies and Articles throughout the forum. There’s a ton of information on all aspects of budgie care, and how to keep them at their best.
Welcome to the forum

. Please keep us updated on your budgie!