I have an infected finger. Amputation?

Well i skateboard. And when i was skateboarding downhill, and surprisingly i fell, road burned my arm, and scraping some skin off my pinky. It has been about 4 days. Today i put hydrogen peroxide on it, and it started foaming, which means it is infected. I have a 10x10mm yellow kind of scab. It is on my knuckle of my pinky. What do i do? I have a doctor's appointment tomorrow. Do i need amputation? My infection is yellow colored.