Hi! I'm sorry that you're going through this. You're definitely not alone, though. Anything blowing into your nose can cause irritation, congestion, a stuffy or runny nose, etc. It's very common both with CPAP users and people who use oxygen.
Using a humidifier is generally a good idea, since most people complain that CPAP can dry them out, but the opposite can happen, too. Have you tried experimenting with the level of humidity, or turning off the humidifier for a while to see if that calms things down?
I also wonder if using a saline spray in your nose right as you get up could help you flush out mucus so that you don't feel so runny. I'm not sure about this, though.
It can't hurt to experiment with different types of masks, too. What are you using now (full face, nasal pillows, etc)? Maybe a different type would be less irritating to your sinuses.
Lastly, you can always ask the doctor that prescribed your CPAP what they'd suggest. Maybe an over-the-counter medicine could help, but don't try anything without their knowledge.
I'm glad it doesn't last all day at least. Keep us posted on what you can figure out, if anything! -Melissa, team member