I am not constipated but at the end of my bm i feel that there`s a part that won`t come out. can a 23 year old have colon cancer?

YES: Colon cancer can occur in any age group. However, it is most likely something much less ominous. Often times, having an internal hemorrhoid or small anal fissure can cause similar sensations. It is best to get it looked at, as ruling out the worst case scenario is the best approach to avoiding bad outcomes.

Yes: It would be inordinately uncommon, but a 23 year old can have colon cancer. To be sure you are not missing anything, see a doctor and be examined.