I have an old Nikon FG?

And i by accidentally popped the part that holds the film. I didn't expose the film at all. It just popped open. Do you think i ruined my film?

Were you indoors? There's a possibility that only about three of your images were damaged

If you were outdoors, then the damage to your film could be more extensive

There are cameras still using films?

Most probably yes and there's only one way to find out. Have the film developed.

I know you damaged the film. 3 images will be total lost, many will have light leaks on the edges.