Elizabeth,
I too remenber feeling a "new" lump a couple of years post treatment. It turned out to be scar tissue and I was reminded to do daily neck exercises to prevent "wooden neck". Here's hoping that you get the same news.
All the best,
Rob

6-05, Left Tonsil-T1N2bM0 stageIVA, chemo(Cisplatin), radiation(6660cGy), neck disection, no PEG. HPV negative. (Doc suspects posit)
3-9-09 last of 30 HBO treatments.