What problem is this?
It's toothache.
What's the matter with him?
runny nose/blocked nose
What is wrong with her?
cold
What problem is this?
It's a runny nose.
What's the matter?
headache
What problem is this?
It's stomach ache. / It's an upset stomach.
What's wrong with him?
stomachache
What's the matter?
toothache
What's the matter?
He has a headache.
What problem is this?
It's a sore throat.