In perusing my "Chicken Health Handbook" sinus discharge is linked to a wide variety of bacterial or viral infections. Some are mild and will pass in a few days or a week. Others are severe with high mortality and pose a public health risk.
Without knowing more symptoms it is impossible to speculate what is wrong with Homer. However, I'd isolate him from your laying flock until all symptoms pass and he is back to his regular self. Be sure to look at your other chickens for similar symtoms. That he wasn't with the hens last night raises red flags that he's not feeling well. I've found many animals disappear for a day or a week and then come back with some badly progressed injury, disease, or infection. It seems to be natures way to keep a sick or injured animal away from its home/group to keep that group from harm.
Search on this site and on the internet for chicken respiratory diseases.
Good luck!