I agree, if you perforated an intestinal wall, you will know within a few hours. Basically it would be the same as rupturing an appendix, 'and life threatening', as your waste products wound be escaping from your intestines and into your body, which will cause a great deal of pain!
Feel that, then best to get to the ER immediately! And no matter how embarrassed you would feel about it, tell them exactly what you did, as by that point, they're going to be saving your life...
The lining of the intestines are delicate, and are easily damaged and perforated. And actually the smaller you go with something, the more dangerous it could be.
Doctors when performing a colonoscopy uses a scope that is 6 foot long, and about 3/4 inch in diameter. But they are also looking through that scope, and have the ability to turn it and guide it through all the turns and bends in the intestines.
A small drop of blood could come from a hemorrhoid, or a scratch of an intestinal wall, especially when going around any turns or bends in the intestine.
It is for sure something to be cautious with...