First, I hope you weren't making salsa in an aluminum pot. Tomatoes are acidic and can react and give a nasty taste with aluminum pots.
Second, the official and safest practice is to throw it out.
However, I personally have health problems and often cannot do my canning in one straight shot. This means I leave a pot full of X on my kitchen counter overnight and pick up where I left off the night before.
I BRING THE FOOD BACK TO A BOIL ALWAYS ALWAYS ALWAYS. Bring the water in the canner to a boil, too, re-sterilize the jars, re-sterilize the lids, the screw-on bands, I do all of this so that everything is just as it would have been without the interruption caused by my leg/knee pain the night before.
Sunset Zone 17, USDA Zone 9