It is most likely a lymph node. I have one that grows and shrinks in the same spot. They usually get larger when they are fighting off infections. Do you possibly suffer from acne? I went to the doctor and asked him about them and he said the cause could definitely be from acne which is an infection.
Pay close attention to the size of it and if it doesn't get any smaller soon, i highly recommend going to see your doctor. But generally enlarger lymph nodes aren't a cause for concern unless they grow over the size of a half inch.