Combine water, honey, and lavender in a saucepan over medium heat and stir until mixture comes to a simmer. Remove from heat and let steep for 30 minutes. Strain and discard lavender. Let syrup cool to room temperature. Transfer lavender-honey syrup to blender, add blueberries and lemon juice; blend until smooth. Strain and discard seeds and skin, if desired. Process sorbet mixture in an ice cream maker according to manufacturer's instructions. Transfer to a freezer-safe container, cover, and freeze until firm, at least 2 hours.