https://www.dailymail.co.uk/health/article-7093737/British-man-suffers-NINE-DAY-erection-falling-moped-bruising-genitals.html
A 35-year-old British man was left with a nine-day erection after falling off his moped and bruising his genitals. The bruise to his perineum - the area between the genitals and anus - in the crash, nine days before his visit to a UK hospital, caused a constant flow of blood to his penis.
It meant that he was left with a Grade IV erection - the highest level on a medical scale known as the Erection Hardness Score - for nine continuous days. Full story in link above.