<s>[INST] Hi, my son is 17 yrs. Old, lifts a lot of weight with friends, he had a knot appear almost , slightly behind his right ear, local Dr., Said not to worry, but now two has appeared on the back of his neck, which is very small,at the base of his skull, can lifting weights do this [/INST] Hello, It could be lymph nodes enlarged due to some infective process going on the scalp or and in the head. Dandruff is one common cause for it. You may consult a dermatologist. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Nirmal Chander Gupta, Orthopaedic Surgeon </s>