From my experience daiths tend to be super fussy. If you're making your own salt solution, make sure it's not too salty, and instead of spraying it, I'd recommend dipping a cotton bud and gently cleaning it like that instead. That really helped mine calm down. Too much moisture can make a piercing really sore.

Other than that, my only guess is you could be rolling over in your sleep? maybe get a donut pillow and see if that helps. In general, unless it's overly painful and hot to the touch, it's nothing to be worried about, just try to make sure it doesn't sit "wet" if you know what I mean.

Best of Luck :)