The glands under your jaw are lymph nodes. Lymph nodes help the body to fight infections. Sometimes a swollen gland can be as simple as your body fighting a cold, but it could also be a more serious infection. While I would encourage you to see a medical professional, there are a few things you can try to make yourself more comfortable in the mean time. Hot teas or warm drinks might help sooth you gland; it rests along the throat and the heat from a drink will sooth the inflammation. A warm compact might also be soothing, but remember not to wrap anything all the way around your neck. This can create too much of a temperature change in the blood vessels leading to your brain; it can cause a serious headache.
According to what I've read online, there is no specific treatment for a swollen glad or lymph node...because they are usually a sign of some other problem. First that other problem has to be addressed, and when that is cured the swelling will go down.
For example, if the swell is a result of an infection, then after antibiotics cure the infection the swelling will go down.
I highly suggest you go see a doctor to see what is really happening...especially if you are also experiencing a fever, sweats, or weight changes.