If the dough has already come together you can put a teaspoon or so of water on the kneading surface and knead it into the dough.
If too dry, add water, a little at a time (not oil - I'm Italian, and we never make pasta dough with oil). If the dough has already come together you can put a teaspoon or so of water on the kneading surface and knead it into the dough. The dry air in your home could be a factor, or the age of the flour; I doubt you'll ever wind up making pasta dough with the exact same measurements twice.