Hello, Abscess is commonly caused due to infection and is filled with pus. It may be tender to touch and inflamed, red with soreness of the skin surrounding it. Cyst is hard to touch, it is filled with air, little liquid and more of solid material. It is formed due to uncontrolled cell mutation. Often a cyst disappears on its own. If it persists means it has to be removed by surgery. An abscess has to be incised and drained out. it is cleaned and antiseptic dressing done. For faster and better healing a course of antibiotics is prescribed along with NSAIDs, to help reduce pain, inflammation and soreness. Since your daughter is suffering from diabetes she should control her blood glucose level at all cost. High blood glucose triggers infection, formation of boils, carbuncles or abscess. She is suffering from abscess. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician