In a small saucepan over medium-high heat, combine blueberries, sugar, lemon juice, cinnamon, and 3 tablespoons water. Bring to a boil, reduce heat to medium, and simmer until blueberries have broken down and juice has thickened slightly, about 10 minutes. Use a rubber spatula to press berries through a fine sieve set over a small bowl; discard solids. Let cool slightly. Cover, and refrigerate until ready to use.