If you paid with credit card, contest the purchase IMMEDIATELY.
SHortly thereafter, file a claim with the shipper - concealed damage. Typically such claims get resolved 1/3, 1/3, 1/3 (recipient, shipper, seller).
If you didn't mark the bill of lading as being damaged when you signed shipping reciept, you're screwed. Consider this to be an expen$ive learning lesson.
You'll be surprised how fast the seller will try to work things out when the contested credit card thing happens. If you paid COD, hopefully you did it twice - first and last time - for what now should be obvious reasons.