Swollen lymph node behind ear around 1cm size. A bit hurts when pressed. No other symptoms. What is it?

Scalp issue? Lymph nodes in the neck ofter get enlarged due to issue with the scalp, e.g., dandruff. Wash your scalp daily with any shampoo. Check your node every couple of weeks, not more frequently. if it doubles in size or other nodes get enlarged, see a doctor, otherwise watchful waiting is appropriate.