I am not aware of anything that will cover up your scars without drawing attention to itself and you. That being said, you have the following choices:
1) Skip the prom; it's an out-dated ritual that is way over-rated and ridiculously self-indulgent and expensive. Yes, I went to mine, so I know what I felt about it then and still feel about it, lo, these many years later.
2) Go as you are and don't worry about what people think. Know as an absolute fact of nature that not a single person who will be at the prom is even close to perfect, regardless of how well he or she dresses or acts. Be proud of who and what you are; everyone has blemishes somewhere, inside or out or both.
3) Go in a tuxedo. A girl at the high school where I taught went in a tux one year. She was the hit of the prom, and people are still talking about her twenty years later.
4) Find a dress that will be beautifully complimented by a tasteful or flamboyant scarf, whichever suits your fancy.
Hey, in the end, it's a dance, so, if you choose to go, dance and have a great time!