Bleeding after you poop is a very bad sign. It relies on if you are bleeding after, or if you have blood in your poop, though.

Sometimes people have really hard agonizing poop that may tear their rectum. Or occasionally there is something bleeding within and the blood just comes out the rectum.
I am not a doctor, but I'm sure that there's a lot of dangerous bacteria within that area. Not something to mess with.
It is very common to have this issue at some point in your life though, so get it checked out.
A doctor can tell you right away. Hemmorhoids can be easily treated w/ medicine.
Don't let it go!!! You can get colon cancer or other complications, that are miles worse than a little blood.

Many sicknesses and conditions can cause rectal bleeding. Common causes include anal fissures, hemorrhoids, cancers and polyps of the rectum and colon, diverticulosis, abnormal blood vessels (angiodysplasia), ulcerative colitis, ulcerative proctitis, Crohn's colitis, infectious colitis, ischemic colitis, and Meckel's diverticula.

The biggest possibility is you most likely have hemorrhoids. I suggest you read this article to solve your problem immediately..

Thrombosed external hemorrhoid