To make a sugar syrup, bring first 3 ingredients and 3 Tbsp. water to a boil in a small saucepan over medium heat. Boil, stirring constantly, 1 to 2 minutes or just until sugar dissolves. Add pepper slices, and cook, stirring occasionally, 1 minute. Remove from heat; let stand 15 minutes. Discard jalapeño pepper slices.
Process sugar syrup, nectarines, and next 2 ingredients in a food processor until smooth, stopping to scrape down sides as needed. Pour mixture into 10 (2-oz.) plastic pop molds. Top with lids of pop molds, and freeze 1 hour. Insert craft sticks, leaving 1 1/2 to 2 inches sticking out, and freeze 7 more hours or until sticks are solidly anchored and pops are completely frozen.