What Causes Painful Arm And Runny Nose?

My 11 year old son has complained off and on that his arm hurts for a couple of weeks. I chalked it up to sports, shoveling snow or sleeping wrong until today. He can feel a 1 inch lump that is very tender to the touch. I believe its a swollen lymph node. He is not complaining about any other symptoms but does have a runny nose.