Hey sorry to hear you're having lymph node issues. I've been feeling ill for several months now, weight loss, cough, fatigue etc, with lymph nodes swollen above right collarbone (scary!). GPs have done ultrasounds and chest x-ray, said all looks normal and not concerned, but they can't figure out what's wrong with me. Will push for a biopsies if things don't resolve or get worse in another month or so. 

In your situation, perhaps there's no need for the ER just yet, but I would definitely make an appointment with your GP and get it checked out. Most likely it is nothing, but better to be safe - if anything, you'll get some peace of mind!!