What everyone else said. See a doctor -- they can't do much for it, but they can tell you the extent of the injury, and, if necessary, give you a recommendation to a physiotherapist. I agree with Heather (or, rather, her sister by proxy of Heather) -- it looks broken, when I compare it to when I broke a knuckle falling off a bridge when biking (it was only a 1 foot drop, but it was into a front-wheel slurping bog). If not broken, it may have been dislocated, as well.

My advice? Forget about the concert. Unless you string your guitar backwards, I highly doubt you'll be forming chords with that hand in 10 days.

Speedy healing... keep us posted.