Next: It's possible that when you hit the bump, you may have somehow inadvertently knocked the button that changes the odometer reading from its actual mileage to the trip meter. You can download a copy of your owner's manual from the Mitsubishi Owners website at https://www.mitsubishicars.com/owners/login, and this will help you find out how to change the odometer display.
Finally, it's also possible that your jolt may have triggered some kind of short in the circuit that controls the odometer display. If that's the case, you may need additional technical assistance to repair the odometer and reset it to the correct mileage display. For additional assistance, please find an AskPatty Certified Repair Shop at http://www.askpatty.com/search/?type=all&m=30&q=&keyword= and they can help you diagnose and repair the problem.
Please let us know how the problem was resolved!