Your type of scars is suitable to treat with punch grafting. Dermabrasion will make it worse.
Different type of scars treat with different method.
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I don't think this is skin graft. it should be dermal graft. a piece of dermal transplant in underneath the skin. you need dermabrasion to smooth the lump in order to level with the rest of your skin.
Are you sure you had punch graft done? Base on your picture, i dont see any graft.