I have a swollen lymph node under my jaw. saw doc, said it was firm but movable. it is larger than 1 cm. dark, burning spot on lip same side of lymph.

Be concerned: Inflammation or tumors of the lip will involve lymph nodes under the chin or along the lower edge of the mandible. Most nodes are < 1 cm and soft. It could be as simple as a cold sore or as bad as a cancer. If there is no improvement after a couple weeks or it continues to worsen see md.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.