This clump of blood came out from my vagina post delivery. Should I be concerned?

Having blood clots and bleeding is pretty normal seeing that you just gave birth to a new life. Let's face it, it's going to take a while before your privates go back to "normal". But such post natal bleeding is not anything to be worried about. Passing blood and clots ( could be lochia) is part of the natural process as womb shrinks back to its normal size and your body recovers. Some older relatives of mine call it "getting rid of the old blood".