Broke 5 ribs falling down stairs. a week later my testicals are swollen. why?

Possibly 2 reasons--: 1): bleeding and swelling from the ribs gravitating towards the scrotum over a period of 5-7 days, which is probably the main reason; 2): or you might have hurt your groin/scrotum and because of ribs being more painful and had your attention, the groin problem is showing itself now. I believe the (1) is more likely the rause. See you pcp, or maybe get a u/s for it to confirm no local problem.