How To Remove Sore And Red Bumps From Forehead, Legs And Arms?

My 84 year old mother has a large reddish bump (more like a growth) on her forehead which popped up quite quickly. It is round and about the size of a pencil eraser, with a scabby center. She says it is very tender and sore. She has also had these on her lower leg and on an arm. Those bumps have eventually gotten smaller and gone away, for the most part. But this one on her forehead is of concern to both of us. I do have an appointment for mom with a dermatologist next week, but meanwhile we are worrying. What does this sound like? PS - Mom is 4" 10", 101 pounds, and is a kidney patient.