After exstraction, blood clot can be unseen in whole, where tooth was?

Let it heal: An extraction socket heals from the bottom up. Unless there is severe pain involved, simply the visual appearance of a socket isn't am indicator of a complication. It will fill in over time.

Blood clot in socket: After your tooth is removed, you will see a dark, clotted blood in where the root used to be; a socket. The clot is red, then becomes dark red. As the blood breaks down it will keep changing the color to yellowish, grayish tone. Eventually, you will see a whitish cover in the socket. This color-changing blood clot is a nature's bandaid over the wound. Keep it clean but careful not to dislodge it.