Severe burning using bottle rinse

I’ve used the bottle with your packets and distilled water for years. It’s been the answer to the majority of my headaches and a lifesaver such that I proselytize the benefits of sinus irrigating to everyone. About three months ago, I started experiencing severe burning in my nasal passages when irrigating and have tried a couple of times since then and it’s still too painful, I did use a new bottle recently, and about a month and a half prior to the burning, I had COVID. Why has it suddenly changed? Will I ever be able to irrigate again? I really miss having headache relief without taking pain medication 🙁