Thanks for the query.
Infection is invariably very common in cancer because of decrease in immunity. Lymph
nodes could be due to infection or metastasis. This can be confirmed by investigations, antibiotics need to be given on the basis of microbiological studies. Your Physician will look into all these and prescribe appropriate antibiotics. These infections are treatable and hence not life threatening.
Kindly take the opinion of treating doctor and give proper medication. The surrounding area of infection needs to be cleaned using either Spirit or Dettol/Hydrogen peroxide