Wiper keeps hitting the side of the windshield Edge and car

It could be that the arm is bent, especially if you live in an area where you get snow, as it can cause a higher load on the wipers. A quick check to see if it is bent is to look at where the blade and arm set when the wipers are off. Most windshields will have small marks in the inner layer that show where the wipers are supposed to be when they are in the park position. They can be hard to find on some and out in the open on others. If the glass has been replaced they may not have them though. In that event most wipers will park in line with the lower trim line on the windshield.
The other thing that can happen is that the bushings in the wiper transmission arms can wear and the wipers move farther than they should. An easy way to check that is to gently try to move the arm with the wipers off. It shouldn't move more than a quarter of an inch. If it moves more then you need to look at those bushings.
Lastly the nut that retains the arm could have loosened, however your description sounds like the blade or arm have bent, usually if the nut loosens the tip of the blade will hit first.