I have newly formed scars with small blisters forming from necrosis on breatst after a mastectomy ?

Depends: May be as simple as blistering from tape, may mean ischemia of flap, could even mean recurrence of cancer--depending on how long after e surgery it is.

Observe wound care: Depending on the wound tension and potential for infection, observation is typically advised with a topical cream such as silvadene (silver sulfadiazine) cream. Healing will likely ensue, possibly with a slightly wider scar. In other instances of obvious tissue necrosis, your surgeon may elect to excise the compromised tissue either early or in a delayed fashion. Keep in close contact with your surgeon to monitor wound.