Yes, you should be able to fix it yourself. Here is a video showing someone using liquid pvc for a window repair. The repair is not the same as yours, but it's worth watching the video to see how easy it is to work with this product: VinylDoc

If the window is only 3 years old, it is very likely covered under some sort of manufacturer's warranty. I would start with the building management or by looking for a serial number on the window. See if you can get the sash replaced under warranty.