I'm Desperate For Advice And Would Be Super Grateful For

I'm desperate for advice and would be super grateful for any. My dog had a small lump on her back last week, fast forward a couple days and there was a matted blood where the lump was. I gave her a bath and washed all the dried blood away and found what looks like a hole in her skin. It's still draining with blood. She hasn't really changed in temperament or energy. I have no idea what this is or how to treat it. I took 3 months off of work bc I had a baby in May so money is super tight so I dk if I can take care of this at home or if it's an absolute vet trip.