Should i be worried????

Ok so here's the problem... last night when i went to change my sons diaper i noticed that he had a little bit of blood in his stool. When i wiped him there were little streaks of blood on the wipe as well. He didn't seem to be in any pain and he didn't seem to have any trouble pooping. His diet hasn't changed significantly hes been on jar baby food and oatmeal/rice cereal for a long time. I've noticed the past week that his poop is getting harder almost like little pellets or harder turds and not so soft and runny... Has anyone had this happen before? should i be concerned about the blood? hes also had a cold lately could that have any effect on his poop?

I was in the ER yesterday for this because DD had blood in her stool. She has like baby hemorrhoids which is expected because she has been constipated. When I called the nursing line they said what it probably was but they said they don't take chances with blood and had me bring her in.
I don't think it's anything major but I would bring him in to get looked at just in case.