The white dots on nails are known as Leukonychia. These dots form for the following reasons:
1. Nail Trauma:
It might not have been a recent trauma since nails grow slowly. So, the white dot might actually form several weeks after nail experienced the trauma.
2. Side effect or infection:
Usually the spots go away without treatment as the nails grow out. However, if all or the majority of the nails are showing white spots then a doctor visit might be in your best interest.
3. Sign of more serious conditions:
If all nails are showing white spots it could be a sign of anemia, cardiac disease, cirrhosis, diabetes, or kidney disease.