A nail always turns white when pressed, because the blood leaves it. If, after you release it, it has difficulty turning pink again, blood circulation is impaired — for example, the bandage is too tight.
Capillary circulation is checked by pressing the nail until it turns white and watching how quickly its natural pink color returns. If, after you release it, the nail turns pink again slowly and with difficulty, this means that blood circulation in the limb is impaired (for example, the bandage is too tight).
Option 1. Pain points to damage to nerves or tissues, not to the blood circulation that the nail color shows.
Option 2. Discomfort is a subjective feeling and does not physically show a delay in blood returning to the capillaries.
Option 3. A nail naturally turns white when pressed, because the blood is squeezed out; the problem is when the color comes back slowly.