It may be reparable, maybe not - it depends on the extent of the damage. If the socket is all that's been knocked off, you can replace it for next to nothing - but if the board itself is cracked, you may be out of luck. You may - even if the board is cracked, sometimes - be able to hoodwink a jack in by rewiring the board outside the case to a jack by interfacing with the solder points directly.