Dentist said sinus is very congested /inflamed from the x-ray be did. how can he tell? i do have a stuffed nose

Congested sinus: What kind of x-ray did he take? Routine dental x-rays do not show if sinus is congested/inflamed or not. Other types of imaging such as CAT scan and MRI will show that, but not indicated for normal colds and congestion. Perhaps he was basing his conclusions on your symptoms and not the x-rays.

Congestion: A sinus is an opening in the bone, a hole. Siinuses appear dark/black on x-rays. If sinuses fill with fluid/mucous they will appear grey on x-ray. If congestion does not clear within a week check in with your primary care Physician.