I started with plain flour and yeast and realized the flour wasn't sufficient. Without thinking, I grabbed the available flour on my shelf but discovered it was self raising after I had mixed it all. Is that still edible? What will happen to my pizza now? Thanks
In general, if you use self-rising flour in place of plain flour in a recipe for yeasted dough, the result will at best be over-risen. Worst case, the excess chemical leavening will either tear the gluten causing a misshapen or collapsed product. In the case of the pizza dough as you describe it, because you were only adding a fraction of the total amount of flour as self-rising, chances are that you will hardly notice. Because pizza is shaped as a flat disc. it may be a little thicker than usual but probably won't tear. The pizza may end up with a slightly biscuit-like flavor from the baking powder in the self-rising flour, though.
For a recipe calling for 2 cups of flour, you can likely add a ¼ cup or so of self-rising with no significant impact.