<s>[INST] I have a lump in my left armpit that is the size of a nickel, it is purple and fairly painful. I have had it almost a month but haven t had the time to go to the doctor. When i touch it, it feels hard around the edge and the center feels squishy, what could cause this? [/INST] Hi. Thanks for your query. Noted the history and understood your concerns. Lump in the left armpit that has persisted for a month, is of the since of a nickel; purple and fairly painful can be due to the following reasons:Dermatitis with skin changes. Localized hi Chat Doctor. Skin concerts can be diagnosed by the following ways:Get a clinical evaluation and examination by a General Surgeon so that a proper diagnosis may be done and relevant investigations done to see the cause and plan a proper management. Till then apply liquid provide iodine locally. Keep the area  </s>