Welcome! If it has low mileage it may just go away. Others have reported that if the noise is from the injectors it may be gas related and by using only 89 Octane Gasoline or changing the brand of gas solved the issue. If it is oil related using premium oil or a different weight solved the problem, however this was usually in the Winter at start-up. Hope this might help some and please let us know of any resolve. Thanks for your Post and Good Luck!
Nitro Year: 2007 (1 of 91,815 sold in 07)
Nitro Model: R/T 4X4 Stone White
CAT-BACK Exhaust, CAI, Projector Head Lamps
Fully-Equipped w/all factory options