What Causes Painful Bruising On Genitals?

I m pretty sure I have poison ivy or, oak, on my genitals ( I am male) I put calamine lotion on it, and of course that burned a little, but not horridly. I just took a shower, and any amount of water that touched it cause what I would describe as the most brutally painful experience I have ever had in my entire life. Shortly after, I noticed what looks sort of like a bruise. Of course, this has me alarmed. any advice?