Could this be necrosis of the tissue? 7 days after breast reduction surgery. Extensive bruising right after surgery. (photo)

I had what seemed to be a blood blister appear 2 days after breast reduction surgery.The blood blister has since popped and I've been giving instruction to put perscribed antibiotic cream 2 times a day. I was curious to receive any opinions on what this may be and what the percentage might be of it healing on its own or needing medical attention? I was told a skin graft may be a consideration if it is not healing well. Thank you for your time and expertise.