A bent corner like this occurs if the processor was improperly inserted into the socket and the mechanism used to hold the processor in the socket is engaged. This falls into the "customer induced" (i.e. "man-made") damage category and voids the processor's warranty.
If you remove a processor from its packaging and immediately see that a corner is already bent, this is an indication that your vendor has sent you a processor that was previously damaged. In this case, you should send it back to the vendor for replacement. Unfortunately, if you didn't look before actually trying to use the processor, the vendor will have to assume that you were responsible for the damage and likely will disallow the warranty return.