Hi,
It sounds like this is likely related to an infectious cause. Tender nodes are usually from infection, which is less worrisome. If the node is still palpable, keep an eye on it- if it is not gone in a couple of weeks, especially if it is growing, or seems hard and immobile, make sure you have it looked at by your doctor. Other things that should trigger more concern would be unintentional weight loss, fevers/chills/sweats.
I hope it is resolved for you soon,
JMK MD