1. Cut mozzarella into 3/4-inch cubes. Slice each nectarine into 6 wedges, and cut each wedge in half (for a total of 36 pieces; you'll have a few extra). Set aside.
2. Skewer 2 cubes mozzarella and 2 pieces nectarine per wooden pick; place on a serving platter. Drizzle with pesto (thin with a little olive oil, if needed), and serve.