Sometimes Photoshop will select the motherboard GPU. In the Photoshop preferences, under the performance section, does it show the NVIDIA card or the intergrated graphics chip? It will show it next to the “Use Graphics Card” checkbox.
Also, in your windows Device Manager, you can disable the integrated graphics. You should see both devices listed there. Just find the integrated device, right click and select Disable Device. See this screenshot. Note: Mine shows 2 of the same because I have 2 dedicated cards on this computer. Yours will show each different device.