I'm with Schmick, the times I've had chest pain (don't google, it'll tell you it's a blood clot, apparently that's the cause of every chest pain in the world), it's been a pulled muscle or bronchitis.
So worth getting checked out, in case it's the latter.
Maybe take him to the doc the time of day the cough is worst? Often I find early morning and later in the day my cough will be bad, with mucous moving about, and midday/afternoon my chest sounds fine and I get sent home by doctors. Really strange. That's my unmedical, but based on my experience advice. Take with a grain of salt.