There is a blood vein that runs along side the bone.
If the chicken was not bled properly, which most of them are not, it will hold quite a bit of blood and can not be cooked out.
I got a DQ because of this for thighs that temped at 175-180 + because the blood was still there.
For chicken prep, either in comps or at home, I take a moment and run a knife along there. Remove the vein with tweezers and cook on.
Just "ugly", not unsafe.
"Flirtin' with Disaster" BBQ Team (RETIRED)
FBA and KCBS Cook and Judge.
Former owner of a WSM, a Smokey Joe, a Charbroil Commercial gasser (junk), the legendary "StudeDera" and Sherman.
Now cooking with a Fast Eddy PG500
Proud Pellet guy cooking on real wood.