First thought is a swollen lymph node which are plentiful in our neck. Do you feel sick, “under the weather” or have a fever? A swollen and tender lymph node can be a sign our body is fighting an infection (viral or bacterial). Staying hydrated is helpful to flush our lymph system. Of course if it persists for a few days it would be good to have your primary care physician take a look. Hope you are feeling much better very soon!