If you usually wear eyelash extensions, then it may be the eyelash glue which you use to stick the eyelash extensions to your real eyelashes that irritates your own real eyelashes, especially when you do not completely clean the glue when you take off the eyelash extensions. Also, if you usually wear mascara, then it may as well irritate your eyelashes because ther many chemicals contained in the mascara. Another potential cause can be meibomian glands, which is a kind of mucosa infection. In this case, you can apply warm water bags on your closed eyes to reduce the pain. And use some antibiotic eye drops into your eyes. But you still had better go to the doctors' for an examination to find out the exact cause of your eyelash pain, in case of more serious conditions.