*usually* you won't hear a chain going bad, (unless you have links
that snapped, which is highly unlikely), more often the tensioners
wear out and you get slop in the chain which, eventually can make
the chain jump a tooth and throw your timing off.

I guess the slop could be bad enough that you could hear the chain
slopping around but that would be *after* the engine warms up, not
just when it's cold.

Can you describe more about the sound?  Any idea from what part
of the engine it's coming from?  Does it happen when you start the
engine after it's been driven?  Does it happen all of the time?  Have
you opened the hood and listened while someone else started the
car?

How many miles are on it?

I have a 1999 Altima (110,000 km) that has always had a tapping sound for 1
or 2 seconds after I start it, usually only on warm mornings when the car
has set overnight.  I've never been able to figure out what it is, but the
dealer suggested it might be a hairline crack in the exhaust manifold;
apparently that was a common problem with this era Altima.  Whatever it is,
it hasn't gotten any worse in over 2 years of having had the car, so I've
just learned to ignore it.

I did have the valve cover off this summer to replace the gasket, and
everything under there looked brand new; no scoring on the cams, no sludge,
and the timing chain was tight and looked to be in great shape, so that
helps me sleep at night ;)

Hope that helps!

Could it be the hidraulic chain tensioner (if this engine is equipped
with it).  That was the source of such noise in my Maxima.