Meat spots. My hens occasionally lay eggs with meat spots on the yolks like that. If they are really small spots, I just eat them. Sometimes I pick the meat spots out. Other times I will just feed the egg to the dogs.
I see more of them when there is stress in the coop. A few weeks ago I started to get more eggs with meat spots, I noticed a hawk sitting in a tree near the coop. Hawk has moved on and meat spots are mostly gone.