Even for the most toned musculature and taut, youthful skin, 4 months is certainly adequate time for the vast majority of breast augmentation patients to have their implant position drop, soften, and settle away from the "high, tight" look you still have.
To my eye (thanks for including photos, they are very helpful in giving better answers), this is not just an issue of nipple protrusion, but rather what appears to be a Baker 4 capsular contracture. You still look abnormally high and round superiorly (what many would call the "Baywatch look"), and without examination I can only speculate about implant movement (or lack thereof) in your pockets. If indeed your breasts are both firm and move very little in their respective pockets, then you have capsular contracture, and this gives you not only the high round appearance we have been discussing, but puts abnormal pressure on your nipple/areola complexes, causing or aggravating the protrusion you ask about. In some cases, this degree of capsular contracture can also be painful.
If your breasts are soft, then capsular contracture is less likely, and this may simply be slightly too-high position for your implants, or perhaps implants that are a bit too big for your frame and tissues.
You need to see your plastic surgeon (or another ABPS-certified plastic surgeon for second opinion) to discuss this. Occasionally, leukotriene inhibitor therapy (oral Singulair or Accolate plus vitamin E) may help reduce the severity of capsular contracture, but in severe cases, only surgery to release or remove the capsules will offer relief or improvement of this tightness and nipple protrusion. Make an appointment to see your plastic surgeon and have this evaluated and a plan formulated. For more information about capsular contracture click on the web reference link below. Best wishes! Dr. Tholen