abrasion ; graze, cut. An abrasion is an area on a person's body where the skin has been scraped.

Experience: I was riding bike with my dad.
> Experience: I was riding a bike with my dad.

Because my dad ride a bike better than me, he ride faster and faster.
> Because my dad rides a bike better than me, he pedaled faster and faster.

So, I ride my bike faster and faster to follow my dad.
> So, I did the same thing to follow him.

But, there was a edge that is pointed out, so, wheel of my bike trippled, and it overflowed.
> But as I was pedaling , I stumbled when I crashed my bicycle into a (curb)?.

I flew to the ground, and I scrapped, blood was pouring at my knees, my dad comed and cleaned my knees.
> I fell on the ground, and I scraped my knees, blood was dripping from it. My dad came and cleaned my wound.

'The next day, my knees were bruised and scratched.
> Correct!

It was very painful, but it cured quickly.
> It was very painful, but it healed quickly.