Yes, you can use a Freesync display with a Nvidia card, just bear in mind the following points:
As has been said, you will not be able to use the Freesync feature, Nvidia cards don't support it.
What you CAN do is use the Adaptive syc option in the Nvidia Control Panel, this will sync to whatever the frame rate is once it's over 60FPS, then it'll switch to normal Vsync once the FPS drops below 60.
You will notice some minor issues if the frame rate drops into the '40s, just as you would with Vsync, so try to tune each game to keep the frame rate up over this point.