What's the difference?
We've all had these, but as non-natives it's often difficult to not only decide which word is best, but also start moaning about the English language because it has so many words to be the same thing. Well, the eskimos have fifty words for snow.
First, hurt – to begin with, it’s a verb – I hurt myself. To be hurt is when, for example, you fall and have an accident by hitting your knee hard on the ground. We often think of this as a temporary situation, something from which you will hopefully get better from.
However, pain (uncountable noun) is something that, depending on the situation, is more of a continuing sensation, a continuing feeling you get after you have hurt yourself. For example: Ow! I’ve hurt myself on the knee – give me something to make the pain go away!
MICK: You’re holding your arm. Does it hurt?
BELINDA: A little, but I should be alright.
MICK: Okay, but if the pain continues, you should see a doctor!
Now an ache is a continuous pain, but not to the point that it will make you feel very uncomfortable. It is a pain that you experience after, for example, when you’ve been exercising too much: Oh, I’ve got so many aching muscles!
If you’ve been eating too much: I’ve got stomach ache!
If you've got some kind of medical problem: I've got stomach pain!
Or you have a bad tooth that is giving you toothache.
But if the toothache is getting very bad, then you should see a dentist as you are now experiencing a lot of pain.