If the lump is actually on the neck, it sounds like an infected
abscess....They are extremely painful! She (The
dog) needs to see a Vet to have it drained......Oral antibiotics are needed to keep the infection from spreading into the system, from the toxins......
If the lump is farther down between the shoulder blades, then you may be dealing with something completely different......Tumors are prone to that area & it needs to be removed quickly......