Its very common for there to be slight fluctuations in the rotor(disc). Just as wheels tend to never be completely true after some riding with V brakes.

My Rotors rubs my brake pads all the time, its just the nature of the system. When you repeatedly apply pressure to the rotor, it will begin to flex and go out of true.

If it really bothers you, you can try and true the rotor, but if its only a slight bend I really wouldn't worry about it. The caliper(the brake) was attached to the bike when the rotor was true, so if it was installed to torque spec, which it likely was the caliper is in the correct spot.

Id just ride the bike and the problem very well may resolve on its own. Sometimes after you have a long day of constant braking, the rotors get so hot they kind of self true themselves.

 

BeaverTail nailed it but because you said you dropped of a 3 foot ledge before it started I would check the QR's to make sure there tight and your wheels are in nice and straight.

I dont think I have ever seen a rotor perfectly flat (even new ones) and you can usually move your caliper to keep the pads from hitting.

I have a specialized hardrock disk bike. My problem is that I recently noticed that when I was riding, I can hear my disk just slightly scraping the part where it stops the bike. I tried loosening the brake cable but that didn't really help, all it did was make my brake lever lighter. I don't know If it was because I dropped off a 2'-3' ledge. maybe I bent the disk. It only scrapes at a certain part of the disk.

If you need pictures, let me know and I can take a pic.

Please help me