I have a doubt of using article a before pain.As pain is not countable there should not use article a but mostly book used article "a".can any one explain why?
Pains can be of different kinds (and we feel them in different places). For example, we can experience burning, throbbing, cramping, and dull aches, and can have pain on the skin and pain in the belly or in the knee. So we are at liberty to use the article, and we often do:
Doctor, I have a throbbing pain in my right temple.
The patient presented with throbbing head pain.
I haven't taken great pains to answer your question, but can elaborate if anything is unclear.