Spano is right. It is the CNG Fuel Injectors which produces this sound. Nothing to worry. The only care you can take is that do not ever wash your engine at some normal car wash. Always take your car to Suzuki Authorized workshop 'cause they have the proper covers to cover the Injectors and then they wash the car or you can use petrol to wash engine.
Dont worry about what they say, if they insist on some problem then "Gur Kha kaiy un par char Jao" and screw them dry (sorry for the foul language) but believe you me that works. I did the same to Honda managemnet over here at Lahore when my brand new Reborn had issues with the suspension on the day 2 of delivery.