Hello, Rosie.
First of all, it's good that the scar is "pinking up." Bad news is, it won't be gone by Tuesday. Even if you use an expensive scar-reducing cream (such as Mederma), it can take WEEKS for it to fade. Your best bet at this point is to either wear long gym pants, or use a durable water-proof cover up. Wish I had some better news for you.
Best of luck!