when you say cursor, do you mean the mouse pointer?
If so, don't worry, i think you may have activated the zoom feature within OS X!
It's easy to zoom in and out. I assume you have a scroll wheel on the top of your mouse?
Ok. hold down the Control key and scroll forward (using the scroll wheel/ball on top of your mouse). You will now zoom in to your screen. Releasing the control key and moving the cursor will move you round a very zoomed in screen.
Holding down control key and moving the scroll wheel backwards will zoom you out. When you can no longer make the background move by moving the cursor or you can see the full screen you are back to 100%....
Let us know if this helps...