In a medium saucepan over medium-high heat, combine fresh blueberries, granulated sugar, ground cinnamon, and a pinch of nutmeg. Stir continuously for about 10 minutes until the sugar dissolves and the blueberries soften, retaining their juices. Remove from heat and let cool to room temperature.

In a large mixing bowl, combine heavy cream and sweetened condensed milk. Use an electric mixer on medium speed to beat until light and fluffy, forming soft peaks in about 3–5 minutes.

In a freezer-safe container, spread one-third of the whipped ice cream base evenly across the bottom. Dollop generous spoonfuls of blueberry filling over the ice cream and repeat the process, ensuring the last layer is the ice cream base.

Gently swirl a butter knife through the layers to create a marbled effect and avoid heavy stirring.

Cover the container tightly and place it in the freezer for a minimum of 4 hours until solid.

Before serving, let the ice cream sit at room temperature for about 20 minutes for easier scooping.