Many women will experience an increase in the sensitivity of their nipples following breast augmentation. But for most, this increase sensation will generally subside over time and normalize. If you experience significant sensitivity or even pain to your nipples after the first year, there is probably something else going on.
First, you may have a degree of capsular contracture. However, this generally causes discomfort to the entire breast and is usually on one side only.
Next, you may have a ruptured implant. However, the likelihood of both rupturing at the same time is incredibly low.
Finally, this change may have nothing whatsoever to do with your implants and may be related to your native breast tissue.
To best determine what is causing this and to effectively treat it, you are best off to see a local Board Certified Plastic Surgeon in your area and have he/she examine you to rule out the obvious possible causes. If no cause is found, then a mammogram followed by an ultrasound or MRI might also help identify a cause for your symptoms.
I hope this helps!