Whether you've added too much salt or too much sugar, there's no going back. You can attempt to mask the flavor, but in your case all you'd end up with is a sweet, fishy tasting relish. (Yes, I've used and currently have Thai Fish Sauce.)
You'd be better off, and much more satisfied with your final product if you just accounted this as a learning experience, and begin again, this time adding strong or questionable ingredients in stages and tasting as you go.
"Food is our common ground, a universal experience." - James Beard