Hii, I am AAAAAAA raj, 18 years old. 3 days ago , I have donated blood in a blood bank for the 1st time, it was a voluntary donation, but now I am worried as I am observing some clotting / black spot in the area of my hand from where blood was taken and its is in almost a round shape of 1 cm radius.Can some one explain me please? I am really worried about it.