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

You just delivered? I think it's lochia. According to this article (http://sg.theasianparent.com/lochia_postpartum_bleeding_singapore/), Lochia will change from bright red, to pale brown and finally to yellowish white. While it typically stops one month after delivery, for some ladies, it could last till 8 weeks.