You don't happen to still have the shed? I always check my sheds to make sure the eye cap is on there, if it's not I wait for another shed since one retained eye cap isn't the end of the world. If you could check the shed you'd have a better idea if it happens to have the eye cap on it.
Short answer: yes, this can heal itself. However the snake will still most likely lose the function of the eye if the original eye cap is gone.
Long Answer: if something more complicated than mechanical trauma caused the eye cap to fall off that could be the sign of a deeper infection and medical care in the form of antibiotics may be needed.
In either case a vet trip would be wise due to the risk of infection either being there or setting in.
How is his over all behavior? Has he eaten in the past few weeks? For the most part is he bright an alert? Ball pythons do not depend on their sight so even if he ends up blind he will still function, you just need to keep very careful watch for infection (lethargy, wheezing, gaping, discharge of any kind).
Make sure the cage is nice and clean, put him on paper towels for now, no wood chips, no newspaper. Keep the water refreshed every day. Make sure there is good heat and good humidity.