Well, since I've ruled out everything else, there is only really one diagnosis left - you've hurt your finger.   It could be a splinter or a graze.  It might even be a bruise.  Either way, it will involve a long period in hospital.  It's really nothing to worry about, they have a special ward there for fingers, and the staff are fully trained in dealing with all manner of digit abrasions and thumb strains.  They will most probably pump you full of paracetamol and poke you with sticks until you're better.  The stick thing isn't really part of the cure, but the days are long and drab in the finger ward, and it does help to alleviate the boredom.

Of course, if it's a paper cut, you're done for.  Sorry, but there is no cure.