Since the swelling has appeared bilaterally (both sides), it is actually a good thing. His body is fighting a stessor, a bacteria or virus and the lymph nodes are collecting the dead cells, or the immune response casualties like it was designed to do.

Our bodies fight off infections constantly, it is when they are not doing their job that we feel the symptoms of the infection and they become out of control.

I would still take him to the doctor to evaluate the cause of his immune response. He may have a cold/flu coming in the next 24 hours. Because of the positioning of the lymph nodes, he should be evaluated for strep throat. He may have the infection and just hasn't presented symptoms yet.

Your doctor may able to detect the cause and treat him before he gets sick. Until then don't be surprised if he presents a fever or muscle aches. It was just a rare time where you were forewarned of a normal childhood bug.

Hope this helps!
Shyla RN