Thanks for posting your query at DoctorSpring.com
I am Dr. R.K and I am pleased to assist you.
It is unlikely to be rectal or colon cancer.
The bleeding you had was for just one day and it was associated with abdominal cramps and loose stools.
It is very likely that you have developed colitis. Infection is the most common cause.
You can get a stool analysis done.
Take a course of antibiotics like oflaxacin and ornidazole along with probiotics.
If the symptoms persists or if it is recurrent, then you get a colonoscopy done to find the cause.
I hope that answers your query.