The 22-year-old Aaron confirmed that the injury was discovered on Thursday evening, following which the decision was taken by the selectors.
"It is a stress reaction on the [lower] back. It was discovered yesterday evening," Aaron told rediff.com on Friday.
The up-and-coming fast bowler had impressed with his pace during the recently-concluded Test series against the West Indies, which India won 2-0.
He also featured in the five-match series against England, which India won 5-0.
Aaron and Umesh Yadav's entry had given the Indian bowling attack a new lease of life. The two bowlers are capable of bowling consistently above 140kmph and many felt they would enjoy the conditions in Australia.
Thus, it was but natural that Aaron was dejected, though he chose to "take the positives out of it".
"It is certainly disappointing, but I am taking the positives out of it. I will train harder for the next month-and-half and try to comeback harder."
Asked whether he would require surgery, Aaron replied: "It is not a serious injury and won't require a surgery."
The Jharkhand pacer also indicated that he will be fit in time for the tri-series in Australia, also featuring Sri Lanka [ Images ], that begins on February 5.
"It will take six weeks to recover and I am hoping to be fit for the tri-series. I will report to the National Cricket Academy [in Bangalore] to begin my rehab," he added.
Aaron is the second player to be ruled out of the tour with injury. Praveen Kumar [ Images ] had to opt out of the four-match series with a fractured rib and was replaced by Abhimanyu Mithun [ Images ].