Yes, it has to run its course. It is a virus carried by mosquitos. We can't kill most viruses in people so we sure aren't going to find treatments for chickens. I don't believe my egg production dropped at all. I don't keep records but would remember if it had dropped severely.
It's really not anything to worry about, kind of like chicken pox in kids, they get it, it goes away, then they won't get it again.
Watch for secondary infection -- you would see swelling, maybe pus, and redness. The one I had that got this was being pecked by the others so I had to serparate her for a couple of days, and I smeared some more Neosporin on her.
Ah, the pain killer myth again. Neosporin with pain killer will not hurt chickens. What will hurt them is any ointment or cream with a "caine" drug in it. These drugs are fairly common and have names like cetacaine, benzocaine, novacaine, etc. -- they always end in "caine." The pain killer in Neosporin is from a completely different drug group and is safe for them.