I had a small tender spot on the back if my head two weeks ago. It appeared to be infected hair follicles, so I pulled the hairs out. The next day, the area had grown to the size of a marble and was hard. A day or so after, it was the size of a silver dollar and soft, and red. I thought it was infection, so started treating the area with apple cider vinegar, and the area shrunk. It has been about a week of treating the area with Apple cider vinegar, and infection has visibly come from the area. However; the area grows, then gets smaller. Any ideas on what this may be and possible treatments? It is located on the back of my head just above the nape of the neck.