Some yellowish discharge which smells like dead fish came out of my left nostril when I tried to below my nose this morning. Is this some kind of sinus infection or something more serious? Many thanks.

That sounds like a typical sinus infection (thick green or yellow mucus is one of the main symptoms).

Yes, it sounds like an infection. Bad smell is one of the primary signs, along with the other things described. I wanted to add that unless you take antibiotics, you could develop other problems....Like a polyp. Polyps can form when the body encapsulates the infection.

Get to your GP, or an ENT.

Good luck.

Ex