If the infection is still liquid antibiotics and steroid drops might help, but once the pus hardens, and it probably will, it needs to be lanced and the ball of pus needs to be removed.I'm certainly not a vet, but I have had chickens come down with sinus infections that look just like that photo you posted.
A very simple treatment using steroid and antibiotic eye drops clears it right up.
Here is one that I did for a friend. Antibiotics and drops will not treat these.