As MRG said, go seek some help. I'd go to the dentist if possible or the doctor. I don't know that ER is necessary, but get an appointment sooner rather than later. See a different dentist or doctor if necessary. It sounds like you have a swollen lymph node, which means there is an infection that needs treatment.
It sounds like you may have an infection, it could be due to a wisdom tooth or a bad tooth. It may possibly be an abscess, you need to go to the emergency room you may need antibiotics. Left untreated you could have worse issues.