The same thing happened to me. They were about to insert a catheter, and around six or seven medical interns (both girls and boys) were observing the procedure.
I was scared that I might get a hard-on.
No one explained the procedure afterwards since I was at a government hospital. Once they had left my bed, I tried to pee the usual way, using a bit of pressure. As soon as I did, it hurt like hell, and it felt like my bladder was going to burst.
I was so angry and in pain so I screamed at the doctor: “Huththige putho, meka pururanda wage, ikmanata galawapan yako!”
Everybody started laughing like looking at a joker, and an attendant came and adjusted the catheter pressure.