Swollen lymph node no pain right side back of neck, no other symptoms. Have an abcessd gum for 1 year no pain just pus, can that affect posterior node?

Yes. The presence of swollen lymph glands in the neck reflect 3 conditions. The first is a possibility of a primary lymph gland tumor or lymphoma, Tahe second, metastatic tumor from oral cavity and 3rd, draining infection. Treatment here is to resolve infection at which time node will regress. Other wise bx neeced.