Dear ceegee: You will see us refer a person to a doctor for pain that does not resolve not necessarily because we think it is cancer but to see if the source of the pain can be identified so that the pain can be relieved. Pain is not common in breast cancer. But scar tissue -perhaps from radiation therapy - may cause some discomfort. If the pain gets worse or doesn't go away, you could address it with your doctor but it is unlikely, especially given the negative mammogram, to be cancer.
It's true that the "typical" cancer doesn't cause pain. But it can. So when there's a new finding, whether it's lump or pain, or pretty much anything else, it's best to have evaluated. Pain that comes and goes is even less of concern. What more needs to be done depends a bit on whether the pain was mentioned at the time you saw the doc who ordered the mammogram. In other words, a normal mammogram doesn't rule things out: it's a reassuring part of an evaluation, but when there's something going on, it's important to have a good physical breast exam, and a plan of followup assuming nothing is found. Seeing your original surgeon might be useful, as well.