definitely go to the doctor! You might have just an infection, or this one may have the same problem. As your doc probably explained to you, the lymph nodes is where the body fights off infection and often time those areas get swollen and tender. For example when you have a sore throat due to infection you can actually feel the lymph nodes around your adam’s apple area inflammed, its actually pretty cool! You might feel pain from a surgery, but since this pain is just occuring I would think it would not be related to the surgery. Since they did a biopsy, I would not think it would be cancerous lymphoma, especially in only 3 weeks.