Indians can't be knighted as India is a Republic. Only citizens of the Commonwealth (which includes New Zealand, Australia, West Indies), of which the Queen is monarch, can be knighted (and use the title Sir/Dame).
The Queen may honor citizens of non-Commonwealth countries with the KBE (Knight of the British Empire) title, which honorees are permitted to use as a suffix to their name.
E.g. Richard Hadlee, New Zealand citizen, knighthood conferred upon him, is now Sir Richard Hadlee.
E.g. If Nelson Mandela, South African citizen, were to be honored with KBE, he would become Nelson Mandela KBE
The Queen may honor citizens of non-Commonwealth countries with the KBE (Knight of the British Empire) title, which honorees are permitted to use as a suffix to their name.
E.g. Richard Hadlee, New Zealand citizen, knighthood conferred upon him, is now Sir Richard Hadlee.
E.g. If Nelson Mandela, South African citizen, were to be honored with KBE, he would become Nelson Mandela KBE
