WOW... just wow.
There's no way in HELL I'd EVER let a nurse get a way with that sort of treatment. Ever. Just like a nurse has every right to confront a rude or disorderly patient, a patient also has the right to confront a rude or disorderly nurse.
I would tell her right away that I did nothing wrong, and that her behavior was inappropriate, unprofessional, unnecessary, and constitutes assault. And I would warn her that if she ever did something like that again, I would report her to her supervisor, hospital administration, and the local authorities. If she attempted to retaliate later, I would document each incident and present it, under oath, to the medical board and / or civil court. I'd make her life hell. I'm a fair, decent, reasonable guy, but I am NOT the sort of person to fuck with.
I'm sorry to sound so angry, but the actions of that nurse are just another ugly example of the misanthropic attitudes, male bashing, and body shame that have become far too prevalent in modern society. And I'm just sick and tired of it. I'm fed up. If a nurse was providing intimate care for me and I sprouted wood, I wouldn't say a word. I'd just keep my mouth shut and let her do her job. But APOLOGIZE??? Be ASHAMED or GUILTY because I'm fortunate enough to have a body that still works the way that God and nature intended??? I REFUSE to feel or express shame and remorse for being a normal, healthy human. Fuck that shit.
If a nurse can't deal with an occasional erection without anger or disgust, let her go sell used cars or something. She has no business being in medicine.