<s>[INST] I'm 16, 140 lbs, and 5"8'. I woke up thursday with a small red lump on my left forearm just below my elbow crease and today it has gotten larger and it hurts really bad. the lump has risen and is hard all around it and has a red rash extending about 2 inches in each direction from it. what could it be? [/INST] Hi.You have explained about a boil turning into a stage of cellulitis which is spreading fast. Get your blood Sugar checked.Consult a Doctor as you need to take prescription based antibiotics and anti-inflammatory medicines. Apply liquid povidone iodine to the whole area. </s>