Preheat oven to 325°F (163°C). Wrap the outside of a 9-inch springform pan with two layers of heavy-duty aluminum foil, coming up the sides at least halfway. Lightly grease the inside.
Combine graham cracker crumbs, sugar, and nutmeg in a bowl. Stir in melted butter until the mixture resembles wet sand. Press firmly into the bottom and 1 inch up the sides of the pan. Bake for 10 minutes, then cool.
Beat softened cream cheese on medium speed for 3-4 minutes until completely smooth and fluffy, scraping down the bowl as needed.
Add sugar and mix until incorporated. Add flour, nutmeg, and cinnamon; beat just until combined, scraping down the bowl.
Add eggs one at a time, beating on low speed after each addition just until the yellow disappears. Avoid overmixing to prevent cracks.
Pour in eggnog, sour cream, and vanilla extract. Beat on low speed just until smooth and uniform in color, about 30 seconds to 1 minute.
Pour filling over the pre-baked crust. Tap the pan on the counter 3-4 times to release air bubbles, then smooth the top with a spatula.
Place the foil-wrapped pan inside a large roasting pan. Carefully pour hot water into the roasting pan until it comes about halfway up the sides of the springform pan.
Bake for 55-65 minutes, until the edges are set but the center 2-3 inches still jiggles slightly when gently shaken. Do not overbake.
Turn off the oven and crack the door open about 4 inches. Leave the cheesecake in the oven for 1 hour to cool gradually. Remove from water bath, remove foil, and cool on a wire rack for another hour.
Cover and refrigerate for at least 4 hours or overnight before serving. Remove from the fridge 20 minutes before slicing for best flavor.