What seems to have happened here is that the contacts on the sides of the plug are aligned with cut-outs in the socket, which has allowed them to spring out far enough to prevent removal.
If you can easily reach the socket from behind, feel around it for the spring contacts. Squeeze them in with one hand while wiggling and pulling the plug with the other hand.
If you can't get to it that way, find 2 stiff thin pieces of plastic which will slide between plug and socket from the front. Each of these should be about 20mm or 3/4" wide. Slip one in and feel where the plug's side contact is. slide the plastic back and reinsert it while trying to keep it centered on the contact. The plastic shim should reach about 32mm or 1 1/4" deep from the face of the socket. Do the other side similarly. Wiggle and pull and the plug should come out.
If the plastic bends, you can use metal instead but first pull the fuse for that socket and test that it is unpowered by trying the cam or by looking at any indicator LED which may be on the plug, If this method fails you'll probably have to disassemble the socket by unscrewing it's outer sleeve from behind. You may have to disassemble what it's mounted in to gain access. Again be sure the fuse is pulled and work gently.
In the future remember to align the plug at least one quarter turn from where it got stuck which should prevent a recurrence.
Phil