@mimifeels It is not uncommon for many us to have a little trouble with the 7% saline. After 3+ years, sometimes it still bothers me.
Here are a few tricks that have worked for me:
Start slowly, I mixed 3% and 7% at first. Started with half of each, and gradually increased the 7% until I tolerated it. Even now, if I have a sore or scratchy throat, I sometimes mix them.
Make sure I am "huff coughing" - forcing a regular cough can be irritating.
Drink extra water before and after nebbing to help lubricate my throat.
Take half teaspoon of honey after nebbing. Or drink a cup of "Throat Coat" Tea by Traditional Medicinals - available in most larger grocers, some WalMart SuperCenters and on-line. Or use soothing throat lozenges (not cough drops) - I like Ricola.

Have you tried any of these tricks?
Sue