This condition can be a kind of purpura. Do get your father to contact his physician for further evaluation and treatment. Because it should be examined to determine the condition and the cause. Seriousness of his case depends on the cause.
need more information like: is your dad obese? has leg swelling? does he have any disease? is he taking any medication? is he smoker? what does he do?? for how long these dots and how big they are? do they balnce if you put pressure on them???