I had the same sort of pronlem not that long ago (well, apart from the fact that I suddenly got the sharp pain while I was ten pin bowling
)
I eventually went to the hospital because the 'bruising' was getting worse, and I could hardly move any of my toes - turns out that I had an infection in my foot (I mean, I know they stink, but an infection
). One week long course of antibiotics, and it was better.
I'd recommend going to A & E personally, seeing as they're the people who sorted me out
