Found it strange that he would have been able to continue after the severity of 'his collision' with the goal post.

... or why in fact, he would have collided with the post, given the flight of the ball.

https://twitter.com/i/status/1390997417600892929

He was seen to be given a head injury assessment which took quite a while.

Being interviewed after the game there was no apparent swelling etc.

So Derby gained an 8 minute (injury time) advantage during which they would have known that Cardiff had equalized.