Most likely the sound and feel that you experienced was a suture that had dissolved enough that a little pressure on it caused it to release the rest of the way. You should call your surgeon's office and discuss this if you are nervous but chances are it was just a dissolving suture and was ...
It really depends on what kind of augmentation you had and if the same thing was done on both sides and sometimes its because you are right or left handed. If the breast looks different and feels different, it is important to maintain follow up with your doctor and have your concerns addressed...
Some asymmetry after surgery is not uncommon and may have been there before but you are very early in the post operative period, just 8 days it seems. Often times if an implant is placed submuscularly and an implant is lower on one side it may be because the person is right hand or left hand...