Does pain mean danger?
From a physician standpoint, sometimes the answer is "No."
One example, sent by an alert friend, is a lump on the back of the neck, with pain radiating downwards.
This could be an abscess or an infected cyst, but since they didn't mention infection, it is most likely an enlarged lymph node. This is one example where the doctor or nurse practitioner or psychic healer will look at it, say "Does it hurt?", poke it and then be all cheerful while you wonder WHY they have to poke it* after you say, "Yes, it hurts."
A newly enlarged tender painful lymph node is usually a reactive lymph node. It is swollen with cells from the immune system and is trying to heal something in the vicinity. A cut, irritated acne, a cold virus, that shaving accident, a low grade infection, an ear infection. Usually I talk about it and recheck it in two weeks.
The lymph node that will make your healthcare person worry is the one that DOESN'T hurt. A slowly or quickly enlarging lymph node that is not tender is worrisome for lymphoma or for metastatic cancer. Once it gets to 1 centimenter, I am calling the surgeon to do a biopsy. We have lymph nodes throughout our body, but the ones that we can feel on the surface are only in the neck, the supraclavicular nodes, the axillas (aka underarms) and groin. The rest are under bone or muscle, though they can show up on CT scan or xray: enlarged mediastinal nodes along the great vessels and trachea in the middle of the chest.
So pain does not always correlate with the level of danger of an illness. The reactive nodes hurt because they swell quickly, and they usually go down quickly as well.
*They poked it to be sure that it is not fluid filled, that it is firm but not hard and fixed, so not an abscess or cyst, and doesn't feel like a cancer.