it doesn't move and isn't tender, but does have me worried

Hi,
Welcome to the ehealthforum and I am really glad to help you out.

For such kind of lump at the top of neck, few important possibilities which need to be ruled out are of a lipoma, neurofibroma or any other benign tumor which may be causing compression of the nerves as well. To confirm the diagnosis, you need to get an ultrasound of the area done. If ultrasound does not confirm the diagnosis then you should get a MRI spine done.

It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.