I had a full thickness skin graft on my leg it was slow to heal causing more scaring than expected. can i use mederma on it?

Why: If you already bought it ok. If not dont waste your money. Get a silicone pad to cover it and find a way to increase pressure over it with tape or wrapping or a pressure garment. Wear that 24/7 for 3 months until the collagen is mature. Steroid injections are often very helpful as well.

Don't expect much: This probably will cause no harm but it is unlikely to any significant change or improvement.