I have had the same sort of thing for a while now, I’m 15 days post op.
It is my left boob only and like you said near the cleavage area, mine is at the top.
It is completely normal for one boob to be more painful than the other and they will heal at different rates. Look at them as two separate surgeries, as they are. My left has been far more painful than my right, in fact my right doesn’t really have pain now but I’m still getting pain in the left
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