When you're pooping blood it usually isn't a serious problem and pooping blood is most commonly caused by anal fissures or a hemorrhoid.
Usually the anal fissure or hemorrhoid will go away on it's own without treatment but if the bleeding seems to get worse or doesn't go away within a week then I'd advise you to see your doctor about it because in rare cases blood in the stool could be caused by bowel cancer.
But more than likely it's nothing serious but it never hurts to have a doctor look at it and be sure.