What could cause one neck lymph node (cervical) to remain 1cm enlarged for 2 months? no symptoms, freely moveable, not hard or tender

Sounds normal: A few 1 cm nodes in the neck is normal. Many infections, mostly minor (colds, strep throat, dental infection, folliculitis, even facial acne) can cause inflamed lymph nodes in the neck. After the infection is gone, minor swelling of the previously inflamed nodes often persists, sometimes for months or years. Ask your doctor the next time you have a routine appointmen.