I was working on a project when I shorted pin 3.3v and 0v. I thought it would restart like normal, but instead of restarting, it wouldn't boot. Both the red and green leds are solid. I have tried multiple sd cards.
Accept you need a new pi.
Try putting you SD card in another pi and booting that. When it works, put it back into your old pi.
Try booting the old pi, and with a multimeter check the difference between 0 and 3.3v pins. Odds on bet it's no longer 3.3v.
Buy a new pi 3. Rejoice that you have a valid excuse to upgrade. (Yes, the author of this answer wants one but can't, because he can't justify it to himself. Pity him.)
Edit to add: you probably took out the voltage regulator. They aren't hugely robust.