If the hole is pushed outward use a small ball peen hammer to gently tap it back in flat. Then a small finger full of caulk and a small sticker and move on to having fun with the trailer.
As far as drilling too deep. Next time with the drill off find the depth you don't want to exceed. Wrap a small piece of masking tape around the drill bit and leave it sticking out like a small flag (picture one of those toothpicks with an American flag on it.)You'll be able to see the tape as you drill.
edit to add a youtube video link.
Link