If there really is no damage to their vehicle, then I don't think anyone would be upset, and therefore I would think that you wouldn't get in trouble for it (however, if you weren't completely sober when you were driving at midnight I beg you to stop before you get in some REALLY serious trouble or, worse yet, hurt someone!). I promise I'm not trying to lecture you, I just want to do what I can to remind you that driving a vehicle is a dangerous thing (the most dangerous thing most of us in the "Western world" do regularly), and shouldn't be taken lightly (and most of us forget just how dangerous it is until something happens). Just being drowsy while driving can kill you (and maybe a car or bus load of other people) in an instant.

As far as the cost of repairing your car goes, there are a lot of important factors at play here that aren't specified by your question. Is there only one panel of your car damaged? What kind of car is it? What year? Is the dent shallow (and perhaps something you could live with) or deep enough that it is an issue for you? Does your trunk still open and close? Do you have full coverage on your car insurance? If so, what is your deductible?

If you do have full coverage, then you will have to pay the deductible (assuming the cost of the repair is more than that), but then the cost of your insurance will go up. Otherwise, it could be as little as a few hundred dollars and as much as a few thousand - without all of those important details it's impossible to estimate. If you want to provide those details I will try to give you a better estimate.

On the bright side of things, if this experience makes you a more careful driver, then it might just save your life!

There can be damage to their car but since it is a truck it is unlikely since trucks are built that way. If it were a car it could be hidden damage. There is no way to know if there is internal damage to the car/truck. It is best to leave a note. If there were any witnesses or video hidden video cameras, you can get in trouble. A friend of mine had his nsx backed into in a parking lot and the car was totaled due to the aluminum unibody. You never know how much damage there is without looking underneath.

Yes you can get in trouble for hit and run. And to repair your car it should be 100-350 no more than that

any impact, you should at least leave a note with your info.

I was pulling out of my friends driveway at midnight and their neighbors car was parked on the street very close to their driveway and i hit it. It was a truck and i hit their bumper so there was no damage. I checked. My car has a dent on the back corner by my trunk. 4inches big about. How much do you think this will cost to fix? And could i get in trouble if there is no damage to their car?