Thanks for the query.
I dont think this black patch is related to flow of blood.
It can be melasma
, a diffuse darkening of face.
You can apply a depigmenting agent.
Products like melalite xl will be beneficial for you.
Also apply a sunscreen in day.
Please meet a dermatologist
for exact diagnosis and treatment.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.