Does anyone know what this is?

[horatio78]

I found it in an egg I cracked

 

[DobieLover]

It's a meat spot. A piece of sloughed off tissue that got encapsulated in the egg.

 

[TioBollio]

I found it in an egg I cracked

What DobieLover said. Nothing to worry about, they are safe to eat (or if you prefer just pick it out).