<s>[INST] I woke up a few nights ago and found a small lump about a pea size hard in character on the left side of my neck i feel slight pain in the back of my head and have been kind of worried since i found it. If it were something serious could it just appear out of the blue like that? [/INST] Hi, dear. I have gone through your question. I can understand your concern.  You may have some cervical lymph node.  It may be due to some reactive changes or may be due to some other causes.  You should take antibiotics accordingly. If it doesn't respond to treatment then biopsy diagnosis is advised. Hope I have answered your question, if you have doubt then I will be happy to answer. Thanks for using Chat Doctor. Wish you a very good health. </s>