Hard lump near gland on one side of neck

My girlfriend told me she had a lump in her neck, and had had it for a while now. I felt it, it is hard kind of grissly feeling, on the left side of her neck near where i'd expect her glands to be. it is noticable when feeling each side, as the right side appears normal. She complained that sometimes it feels as if it moves and causes quite severe pain to swallow. she can feel when this is about to happen, usually at night, and takes preventative steps such as moving her jaw and trying a few rapid swallows. i'm really worried, she said she'll contact her GP but she doesn't seem overly concerned. she smokes, and occasionally drinks, but i just want someone here to state a few possibilities as to what this could be in the meantime. can anyone help?