Lymph nodes swell when the body has an infection. I had yearly sinus infections until past August when B cells were destroyed by Rituxan along with cancerous B cells (Marginal Non Hopkins Lymphoma). Infection symptoms are immune cells attacking - with no cells, no symptoms I believe. My go-to response to sinus infection is a Z-pack. Heals it in one week. Prescribed by my GP every time I’ve had one. This is a possibility but I would contact GP.