help, angel showing signs of.... something

Hi folks, my Angel has developed something overnight which looks like a
small white puff blocking its left nostril. From my preliminary
diagnosis, I think it may be a fungus.

The spot is just the size of its left nostril, it does not really
protrude past the edge of the nostril. It is white in color but does
not appear to be ick.

My water parameters have not changed, but I did add some phosphate
absorbant media to try and combat some ongoing algae issues.

I plan on treating as a fungus, does this sound correct?