question: My 2 year old fell off her sister s back and landed on the area under the chin. She has a small very dark bruise on the right portion of her chin but more alarmingly she quickly developed a large knot under her chin. This happened two days ago and the knot hasn t gone away. It is very pronounced and distorts her lower chin (double-chin-like). The swelling seems to now cover a lot of the area under the chin and is firm (like a firm double chin) Should I see her doctor or should the swelling go down?