My MacBook Pro won't exit out of iPhotos

I was importing pictures from my Nikon d3200, i had to stop it early, so i pressed the stop importing, and the delete the pictures that you have already imported, then I left. Now, it won't close out of iPhotos and it says it is importing photos, but it said that all day. Since it won't close out, i can't shut down my Mac or restart it. And I can't import the rest of my photos either. What should I do?