I do not think this is a cataract at all. Cataracts are more milky, cloudy looking and do not present as a white dot like you show us here in the pic. I am very familiar with cataracts as my Katie had them bad and they led to her being pretty much blind at 17 1/2 years old when she passed. They looked like cloudly misshapen contact lenses on her eyes.
I really believe this is a Corneal dystrophy -- here is a quote: Corneal dystrophies are characterised by a small deposit of calcium, crystal or fat within the tissue of the cornea. They usually develop in young adult dogs (ie 6-12 months), and present as a white, grey or silver dot right in the middle of the eye (or both eyes). They usually don't have any adverse effects, and don't really affect the dog's ability to see. Here is a picture of one up close (But they can appear different too -- some are a deposit of mineral like calcium, lipid, cholesterol, and can be varied in size or shape):
Eye Care for Animals - Corneal Dystrophy
They can be genetic, can be result of trauma, can be caused by having too high a level of calcium or cholesterol in the blood. Usually do not lead to blindness.
But as others have said -- I am no vet -- best to get to the vet asap and get a proper dx. Good luck! Hope it is something that at least will not lead to further eye problems.