A corneal abrasion is a scratch on your cornea which is the clear and protective covering over your iris. It acts as a sort of window and lens to both protect and help you see. A scratched cornea can hurt a lot if it’s something like sand that’s caught in your eyelid and it’s best to touch it as little as possible. If it is from dirt or sand, flush your eye with water.
If it’s particularly bad, a doctor may give you eye drops that can prevent infection, however, scratches typically heal on their own over time (anywhere from a day to a month). If the scratch is particularly bad, however, you can risk corneal infections, cornea erosion or even scarring of the cornea. These are all of course problems that can lead to vision problems. Always check with the doctor if you think you have a corneal abrasion so it can be properly diagnosed and treated if necessary.