Can tonsillitis or sinus infection cause 1 enlarged lymph node in the neck?and if so why? i have 1 white spot on my tonsil no pain. negative strep test

More likely tonsil: A single enlarged lymph node in the neck is common with tonsil infection, rarely with sinus infection. Remember, the lymph node is a collection of lymphocytes that act as a preventive tissue to inhibit the spread of infection to other parts of the body. If you are asymptomatic and the lymph node does not enlarge, probably not serious. Finally, rapid strep test only rules out strep as a problem.

Yes lymph nodes swel: Infection causes lymph nodes to swell especially the one nearest the infection.The neck lymph nodes would be the closest to tonsils and sinuses. They swell because lymph nodes try to carry the infection away and break it down. Infection could be h. Flu or staph or another bacteria or virus or fungal.Cultures could help and proper antibiotics need to be started unless it is a virus.