Can't remove screen to replace iPhone 4 battery after screws removed.

I had no problem removing cover when I tried to replace battery before. I had the wrong battery and kept old battery. I had a hard time fitting cover screen on. I had to force it a bit. Now, I can't take the screen off to access the battery. I'm thinking of using a popsickle stick to tap the class off a bit to slip the cover off? What do you think? Any other suggestions?