(This phrase acts like a noun. It is the direct object of the verb stopped. This phrase is a gerund phrase.) I stopped believing in Santa Claus when my mother took me to see him in a department store, and he asked for my autograph. (This phrase acts like a noun. It is the subject of the adverbial clause when my mother took me to see him in a department store.) I stopped believing in Santa Claus when my mother took me to see him in a department store, and he asked for my autograph.  It is the object of the preposition for.)
Ive googled 'white in extraction site'(!) and had some conflicting info: 'The white material is the blood clot; your rinsing has merely washed away the red blood cells and left the clotted fibrin material, which is white. This is normal, and is of no concern'. The second: 'White color in the extraction cavity...
It is normal to have a hole where the tooth was removed. The blood clot does eventually disappear and it will take some time for the area to close. In the mean time do as tickle said, keep your fingers out of the hole! Keep rinsing gently with warm salt water. If you are having pain you should go back to see the dentist who removed the tooth.