Cut on anus - could it get infected?

I've not had sex and I've not had constipation so I'm not sure why it's happened but I've got a little blood when I wipe. It's bright red and a tiny amount so I'm not worried but this type of thing usually happens once in a blue moon and this time it's been happening all week.

Do I have to do anything to avoid an infection? I'm guessing it's a tiny cut but I'm paranoid about the fact it's in a germ-ridden place. I've just used water on it and it stung so it's external but is that enough?