Non-visible lump / knot on left side of neck 2 fingers below jaw line

Hi,Recently my husband felt a knot / lump on left side of neck, 2 fingers below jaw line. This knot / lump is not visible, but can be felt when you press with fingers. Normally it is not painful, but pains when pressed hard. We suspected that it might be twisted of muscles due to bad sleeping position / pillow, however its been 3 days and the lump / knot is still there even after applying muscle relaxing ointment and using Heat Pack.This is the first time he is experiencing this, he's almost 30 yrs.I'm very worried... PLEASE HELP!!Thanks.