<s>[INST] My son is 5 years old and a cpl months ago he developed a huge knot on the left side of his head I figured he bumped it playing on the playground and I didn t worry about it until 3 weeks later I notices it was still massive and still there so I called a triage nurse and she said bring him this n this n she said if it goes away don t worry about it. Well the next day it disappeared like completely gone so I didn t worry about it. Well here we are a cpl months later and last night I noticed that spot looked red I asked him of he d hit his head etc and he replied no to all questions of and bout injury so I waited figuring it would go away maybe he scratched it. Well I noticed today at about 330 when he got home from school that he had that massive knot that just appeared over night and when I say massive I mean massive. He says it hurts but doesn t complain doesn t itch no fever no injuries nothing so I m scared and worried and desperate for answers. I called his Dr and they have absolutely no clue what it could be so maybe you do [/INST] Thank you for following up. I need more details, how much cm is it? It could be swollen lymph nodes. This can occur with throat infection, previous rubella in latent form, irritation of head skin, herpes infection(Epshtein-Barr infection, cytomegalovirus, 6 type of Harper virus) etc. Please get himself checked to make sure his lymph nodes are not affected. To begin with, blood test with platelets and clotting, ultrasound of liver and spleen. If he were received changes in blood formula you would better visit hematologist.  Best regards.  Chat Doctor.  </s>