i recently got hit by a frisbee in the lip in PE. the injury was minor,so I really didn'y care until I got home and started to practice playing my trumpet, and my range was pitiful: I could barely hit a c mid-staff, when I could hit a c an octave higher before ;(. My question is, one my lip heals completely, wil my range come back or will I have to start over?

You should be fine. Getting hit in the lip will cause the body to send certain types of cells to help heal. This will lead to stiffening which is what reduces your range. Everything should be fine.

If you want to you can ice your lips a little to get the internal swelling down and then follow it with some warm wash cloth compresses to get blood circulation back into the lips. Do this for a couple of days if you want to.

some ibupfrofin should help with the swelling and pain too, sorry i cant spell... plain old Advil

When your lips get injured, not only does blood go to your lips, but lactic acid as well. That's why your lips get swollen after many hours of playing. Just flutter your lips. I had braces before and used to get hit all the time in the mouth (due to sports). But I developed calluses in my lips so now their like leather. You should be fine.