Well, if you bent the frame it can be a VERY big deal. Fortunately, this probably didn't happen.
In most cases, all that needs to be done is for a few screws to be taken out of the bottom row of the bumper cover that connects the cover to the frame, and a piece of metal needs to be straightened out...usually done with pliers...it's thin metal, which is why this happens to so many of them. Not a big deal at all.
Even if you DID damage the front end of the underside, you may very well have not done damage to the alignment, because this section of the frame is well forward of the frame/suspension contact/support points. In that case it may need a bit more work, but the car itself shouldn't (hopefully) be damaged to badly.
Good Luck
Bill Wagner