I have a flat red spot on my neck. It has grown to nickel size over three weeks and is just now beginning to have minor stinging. What could it be?

Red spot on neck. There is no easy answer to this problem without seeing the spot. The minor stinging sensation would not be characteristic of early skin cancer. Insect bites can produce the signs and symptoms that you describe. Foreign bodies from thorns, etc could also give you the same reaction.