What Causes A Soft Red Lump On The Arm?

Thank you for asking me or encouraging me to ask. I have a chick pea size lump on my left arm, 4 inches below my left shoulder. A few days back it was color less and hard. I presses a few time. It was not hurting. Now it is reddish and soft. No pain when touched or pressed. I have a almond size lump back of my neck. My family dr told , many have that, and it is probably fat deposit. I am 66, 130 lb, small frame,vegitarian mostly, though take chicken these days, pre diabetic without any medication...other wise in good health, very active life .. what could be lump on my hand please...