besides the two "clips" on each end, there are also 8 metal rivets that hold that plastic aero piece in place in the middle. you probably popped one of those out, and now it's stuck and won't go back in (they are a huge PITA). like others said, jack it up and get a light under to see what is going on.
to be honest, that lip is going to take a beating. try not to lose too much sleep over it
