Does the dot show all the time, or only at certain times? As in, when you don't have an app open, do you see it? If you DO have an app open, do you see it? Is it tiny or big? Can you take a screen shot of it and show us?
The only thing I can think of that cause any dots in the viewing of the iPad screen are dead pixels. This is a hardware fault that will require you to take the iPad back to Apple for repair/replacement. Unfortunately, there's no software fix for a dead pixel, that I am aware of although you can try to reset or restart your iPad and see if that helps.
Good luck and sorry for your trouble.
Marilyn