Sounds like he scratched his eye. This can happen from the most benign things like even just rubbing the eye. Being senstitive to light or "myopic" is very common if the eye or cornea is scratched. Also the feeling that there is something in it would indicate he is probably feeling the scratch. I would absolutely take him to see an eye doctor. The sooner the better, as some things contain bacteria that can cause major complications (for instance- certain kinds of tree branches). The good news is the eyes are one of the fastest parts of the human body to heal. Best of luck.