Sometimes even when you think you have all your blacks black enough when you get a print back there may be a few white spots or colored spots on your background. How aggrevating! This has happened to me before so I asked someone on Flickr a while back how to fix it and this is what I was told to do. It is so beyond perfect you’ll do it everytime!
Here is how to do it…. There may be some highlights hidden in there and they will show when you go to print. The best way to make sure all the highlights in the black are black is to show the clipping… This will get rid of any white spots that your monitor may not show you.
To make blacks black open the curves and select the show clipping box
When you select the box it will turn the photo white
Select the black dropper and start clicking on the white places in your background
Keep going until all the white spots are gone
Click ok when you are done and you can see your photo again with the blacker background.
With a soft black brush you can paint over your subject in the curves layer mask (circled) where they got too dark and lighten them up again.