Where is a knot usually at if its around your breast and armpit when could be dangerous?

Don't understand: I don't understand your question at all. If you are tying knots in ropes around your breasts you shouldn't. There is no place that is 'usual' for this. If you are describing a pain as a 'knot' then that's not normal or usual either. Perhaps if you state your question more clearly you will get a better answer, or see your doctor.