Yes if you have a tire filled with nitrogen and it loses some of it's nitrogen you can safely add some air to the tire from a regular air compressor and the nitrogen and air will work just fine together.
There's no need to add more nitrogen to your tires if you lose some nitrogen as you can just add some regular air from an air compressor and be on your way.
The air from a regular air compressor is more than 78 percent of Nitrogen while the rest of the air from the air compressor is Oxygen.
And the rest of the air besides the oxygen is minuscule amount of miscellaneous gasses mixed in naturally.
So you actually do fill your tires with some nitrogen when you use a regular air compressor except it cheaper for air than it is for nitrogen.