It feels like I have a cut along some blood
vessel or nerve that goes from my belly button
to my penis and when I stand up, the "cut" is being pulled open, allowing urine inside. I imagine it being like a fresh cut on your arm. When the skin is closed, it feels fine. if it gets pulled open and salt or peroxide is put on it, the pain is awful. The same happens here. The wound or opening is exposed to urine, which has ammonia in it, which is probably painful.