I hit my arm really hard abut three weeks ago on the sideview mirror of my car. It scrapped skin off, so I kept a bandage on it. A week or so ago I saw a swelling just up my arm, and now I have a hard lump about 1-1/2 inch wide, and it has grown very rapidly from a slight swelling to this big hard lump about 4 inches up my arm from my wrist. I think it is a lipoma...I am making an appt with a dermatologist. Does anyonw know if a lipoma can grow this big in just 10 days?