Hello, I Have Had What I Think Is A Large

Hello,
I have had what I think is a large vein in my left pectoral muscle raise to the surface and become hard and noticeably darker than my skin.
This has happened twice now, it itches and hurts but once I press on it the thing quickly recedes.
I have chest pain regularly but was diagnosed with stable angina, but this large vein has only appeared during rest.