How do I fix the screen on my calculator?

How do I fix the screen on my calculator?

A small table was placed heavily on the screen and now there is a small mark on the screen that is light in the middle and dark in the surroundings. When I type in a number, I can faintly see through this mark, but it gets a bit frustrating, and I begin Calculus next semester. I cannot afford a new calculator and this one is functioning very well. This screen problem is a nuisance!