Suggest Treatment For Lump On Neck
Reactive lymph nodes more probable
Detailed Answer:
I read your question carefully and I understand your concern.
Judging from your description those lumps are most probably enlarged lymph nodes. Now the causes for lymph node enlargement can be numerous from benign ones as a reaction to an infection in the body to feared ones like malignancies.
In this case judging from the quick appearance of the 2nd node and by the fact that there are manifestations of a tooth issue, a probable infection at the site covered by those lymph nodes, I would say that those nodes are benign as a reaction to local infection. So I believe the lumps are not worrying for the moment but the tooth might need treatment by the dentist eventually.
I do not think it is related to the spinal problem he's had, it has no relation with the lymph nodes. It may cause that soreness in the back of the head, but so may the infection related soreness irradiate at times, tough to tell with certainty but temporary treatment for both remains with anti-inflammatories like Ibuprofen.
I remain at your disposal for other question