@abeershaabansyr
If you are referring to the darker shading artifacts around the mouth, this is the result of moving the vertices a little with a low poly model. There is nothing damaged. The smooth original surface was just disturbed a little when you moved the vertices and there are not enough vertices in between to allow for a smooth transition. You can fix this with "smoothing groups." Select the polygons of the entire face and then in the Smoothing group tab of editable poly/edit poly click on "Clear All" and see if that clears it up. You can also try hitting "AutoSmooth" after that if Clear All doesn't give you the result you want.