Spilled acetone on my iPhone 5S
It sounds like you might have removed the protective coating in that corner of the screen and that now you have two options (one of which is better than the other!):


Apply acetone to the remainder of the screen - carefully, so the appearance of the screen is once more uniform in appearance. Then immediately buy a protective film for the phone's screen.
Take the phone for repair, asking for the screen to be replaced.


Option 1 involves no cost since you (obviously) already have acetone. Option 2 will be a fairly pricy repair, as it will involve replacing the entire screen, and there is literally no way you can claim that the damage was caused by anything except for your own actions. Option 2 is the 'correct' way to fix the problem.

The lesson you can take away from this is: be very careful with solvents and cleaning chemicals around sensitive equipment - especially if the equipment has a special finish.