Blood or meat spots are occasionally found on an egg yolk and are merely an error on the part of the hen. They’re caused by the rupture of a blood vessel on the yolk surface when it’s being formed or by a similar accident in the wall of the oviduct. Most eggs with blood spots are detected by electronic spotters and never reach the market. But, even with mass scanners, it’s impossible to catch them all. Both chemically and nutritionally, eggs with blood spots are fit to eat. You can remove the spot with the tip of a knife, if you wish.
From:
http://www.incredible...ggs-and-food-safety#6