I Have A Very Large Lump On My Neck, A

I have a very large lump on my neck, a third of the way away from my chin toward my ear, and and an inch1/2 below my jaw. It is approximately the size of a ping pong ball cut in half and does not appear to be a hard solid to the touch. This has occurred within this day. I felt a tightness throughout the day but was busy and never looked in mirror or felt my neck until now.