My iPhone 4s screen is blue, what's wrong?

HI, about two weeks ago, I dropped my iPhone and the screen went black with blue vertical Stripes, within these two weeks, I have hoped something would change, but it is exactly the same. Please note that I have tried to reset it, and no change, I am prepared to replace whatever is wrong with it, but I'm not sure what it is!? Does anybody know what i need to fix, or any good places that aren't too expensive to do this at? Thank you!!