I only missed a couple nights on stage my entire time on the road.
It was for infected sinuses. It felt like a thousand knives were sticking in my head.
Here's how you get some relief.
Put some water (an inch) and 4T salt in a saucepan or small skillet.
Bring to a slightly rolling simmer.
Make a tent for your head with a towel and from about 18 inches away, gently breathe through your nose. Adjust the distance further or closer but don't let the steam burn your nose.