thank you all for the replies.
I took my car to the mechanic and found out that the nozzles were not in a good condition, so i got them changed. the diesel filter according to him has swelled so changed that as well.
Since the oil filter and oil was changed about a year ago, i thought that they need to be changed as well but he was of the opinion that it should not be changed before 5000km at least, and because i live abroad the vehicle was used for only 3000kms in this year.
He called somebody to bring the spare parts and charged me 1350 for the diesel filter (according to him it is original but it has a white Tape on the toyota stamp, he says it is smuggled that is why there is this tape.)
But after replacing nozzles and diesel filter the vehicle performance has improved a lot. Mileage has improved which was the main concern and pick and sound is also better. I feel satisfied.