Our caresheet doesn't make note of it, but I have seen it around.
http://www.kingsnake.com/ballpythonguide/
Q: Help, My snakes eye has a dent in it!
A: Don't panic. This occasionally happens and can be attributed to the snake being a little dehydrated. Make sure it's got fresh water and a bowl that it can soak in. The dent should be gone with the next shed cycle.
Hope this helps.