This happened to me too.
I went to get it checked by my doctor, and he sent me for an ultrasound. Even before the report came back it started swelling down.
Afterwards my doctor told me that my one of my 'lymph nold' (?...Sorry, I don't really know my scientific terms...) was infected, but he didn't find any major problems with it.
I then told my friend about it, and she said that happens to her and her mom all the time when they eat too much oily food. She recommended that I drink some herbal tea (she's chinese)
i'm not sure if your case is the same as mine, go to the doctors just in case, because everyone's different.
Good luck~