Could it be a screw worm (wolf worm)?

I've been puppy sitting for my sister in-law for a couple weeks now. I noticed last night that she had a knot on her lower neck. I felt around on it and it's not just a knot but under the knot something is hooked on the neck its self. A few days ago I had noticed that the fur was missing in a circle shape. While feeling around on her neck last night I realized that she had a scab under the circle of hair. I pull the scab back a little and it's fleshy under there. Could this possibly be a screw worm or maybe an abscess? I've informed her of the knot but she said not to worry about it. Screw worms can kill an animal if left untreated. But I'm not sure what this may be. I don't have the money to take her dog to the vet and she's obviously not worried about it. Any suggestions?

If you're going to be a smart *** then don't waste my time. Thank You!