how do u get this CONTCAR, in the POSCAR first 23 atoms are La but in CONTCAR the first 22 atoms are La, how do u conform this 

Sorry, I have attached wrong POSCAR. This POSCAR is corresponding to 4.16% replacing 1 atom but my CONTCAR for 8.3% replacing 2 atoms. Now I have attached right one POSCAR.

Dear Shilendra

There's nothing wrong with CONTCAR.  I think this happen because the structure loses  symmetry after relaxation. You can visualize by making supercell in VESTA then you will see the same structure. If you create bonds then  you also will see that the atoms are there. You can try xcrysden.

Hai, Shilendra

As Ashis Kundu said thesre is nothing wrong with ur calculation, it just optimization results like this , u can do further analysis using this CONTCAR   

I have visualized in xcrysden also with bonds but it is showing same missing atoms.

Hai one thing u have o remember, ur POSCAR and CONTCAR contains same number of atoms, so it conforms that ur initial an final structures contains same number of atoms and there is no missing atoms.

Next when u visualize the structure, u will find that some atoms missed at the edges of the unit cell, This due to the loss of symmetry in the optimization process. Just visualize the structure in a supercell of 2x2x2, u will found that atoms will be at their position, that u  are thinking "The ATOMS are missed"   

I have visualized  CONTCAR all atoms are present but only symmetric corner atoms are not appearing at one corner side while the same atoms are appearing at other corner side.

There is nothing wrong in CONTCAR but I want to know what should I do so these symmetric atoms will also appear in CONTCAR. I have done calculations with symmetric tag ISYM=0 and ISYM=2 both. CONTCAR is appearing same in both cases.