Dirty F

So i ordered a big fat juicy steak. Order arrived, i started eating it, no light tuend on, just tele so i didnt really see what i was eating. After a few mins i noticed the sauce looked kinda odd so i moved to the kitchen to look at it in the light.
Half my plate was covered in dark brown blood. The meat had dark, almost black spots in it and it looked like i cut open some veins or something. Im kinda worried now because i ate half of it before i noticed...

Anybody any idea what is it and if i should worry?