A small opening in the penis after coitus is usually related to rough sex, glansitis, narrow circumcision and other factors. 1. Rough sex: too rough sex, too hard, easy to lead to penile damage, resulting in penile crack, and accompanied by obvious pain. 2. Glans inflammation: If you suffer from glans inflammation, and do not pay attention to local care during sex, it is easy to aggravate the inflammatory reaction, and will cause local damage, and ultimately will cause the foreskin of the penis crack. 3. circumcision narrowing: if there is a previous circumcision, resulting in narrowing of the circumcision, excessive erection during coitus, strong pull, easy to damage, and ultimately may lead to localized cracks, bleeding and so on. After intercourse found a small mouth of the penis, it is recommended to consult a doctor in time, usually should pay attention to local hygiene, to avoid secondary infection.