Is this white substance wound that healing or pus? (Photo)

Looks like your wound has separated...since you have implants underneath that incision, best to get seen by your plastic surgeon so your wound can be monitored and treated if necessary. 

Based solely on your photo, it looks as if a portion of your incision has opened. This isn't uncommon. Call your surgeon and discuss proper wound care in order to insure that it doesn't become infected. My best,
Dr. Sheila Nazarian
@drsheilanazarian on Instagram

Congratulations on your recent surgery! It appears as though a small portion of your incision has opened up. Based on the photo, it does not look as though there is an infection but I would recommend calling your surgeon for an appointment to get instructions on wound care. It is especially important to follow your surgeon's recommendation in order to avoid infection because you have implants. Best of luck!