<s>[INST] I have a knot on the back of my head, it appeared about 3 days ago. It started out small and barely noticable. Now it is about 1/2 inch long and 1/4 inch wide. It is very painful and extremly painful when it is touched. Even some area around the knot is painful. I did not hit my head or can think or any other cause to where this knot came from. I had a nurse look at it to day, she had no idea what it could be but, ruled out pimple or infected hair folical. I am having headaches and slight trouble focusing, which in normal for me when I dont get enough sleep. But, it is torture to lay my head down to rest, and if I postion my self where I am not laying on it, it is still painful and very uncomfortable. I am more concerned with what this knot is and how to get rid of it than anything else. Please help. [/INST] Hi, DEar, thanks for your query to Chat Doctor. I studied your query in depth.1-In My opinion the painful knot on the back of your head appears to be a spider bite/insect bite/bedbug bite-with infection-cellulitis at the back of your head.2-Or it could be unnoticed early progressive folliculitis, which your nurse missed.3-I would suggest you to check with doctor, who would CBC, X-ray skull, for to rule out the unforeseen cause of the headache with the painful lump in your back of the head.4-Hope this would solve your query.5-Wellcome for any more questions on new or this subject also... Have A Good Day.!! </s>