My stretch mark split open during breast aug. Any suggestions?

These stretch marks are thinner than skin without stretch marks. These can tear and best if possible is to remove or avoid them if one can.

Without being present in the OR during your surgery, I'm not sure that anyone is going to be able to answer your question except your surgeon.  If he had staff in the OR that you now interact with postoperatively, you could ask them but it may put them in a difficult situation.  Ask yourself if you remember having a stretch mark there, as it is conceivably possible for a very thin stretch mark to split, but you likely would have noticed the very thin skin before surgery.  Another option is to ask for a copy of the operative report, but hopefully you can have trust in what your surgeon has told you since you have already trusted him with such an important operation.  Best of luck with your continued recovery!

I would let it heal and the main thing is to keep it from getting infected so good wound care is important.

YES, Allow healing to proceed as planned. After a few months than re evaluate the area of your stretch mark... 

My suggestion is to do very good wound care to allow them to heal well and reduce the scarring. I find that keeping the wound moist and preventing a scab will allow for the fastest and best healing.  The breast augmentation may be causing the breast tissue and skin to be compressed and thus reduce the blood supply to the area.  Therefore, the healing may be delayed until the blood supply has adjusted and reestablished itself.  Do not worry if it takes longer than you would expect to heal because if the blood supply is compromised by the surgery, it will take typically 2-3 weeks for the blood supply to get to it's baseline robustness.  Once this happens,  if the wound is still open you will see a very dense rid tissue that fills in the wound which is called granulation tissue.  Once this fills in the wound will suddenly close up and heal well.  This is assuming your blood supply is limited.  During this time I have found that if the person does not have an allergy to sulfa that using an ointment like Silvadene cream and wet saline compresses are ideal to keep the wound from desiccating and scabbing so that the newly developing blood supply does not get compromised.   I also really like using Tegaderms to prevent desiccation and allow the skin cells to grow across.  This can be used when there is no oozing and also allows the for the wound to be protected from water exposure, which is not possible with a traditional bandaid or bandage.