You have developed an infection in that area. Oral tablet augmentin 625 mg three times a day for a week. T bact ointment should be applied over the area three times a day for a week. In spite of the treatment if it continues to increase in size after 23 days then you will have to visit a surgeon to drain the bus which is collected inside. If it continues to improve then finish the one week course and this will eventually subside. Also did I will have to be examined later if there is an underlying sebaceous cyst which is getting infected. Hope this is helpful.