Call the contractor and ask him.

And get some second opinions on what the smell is - bring in some non-smoking friends for a sniff test.

New concrete has a distinct odor, building materials "outgas" (release evaporatable stuff into the air), and even carpet and ceiling tiles smell different when new.

What provisions for drainage were made along the below-grade area, and what kind of waterproofing is on the outside of that wall.

Mold needs moisture to grow, and the few dangerous ones need SOAKING WET cellulose-based materials.

I would also get it checked out- but I think what you're getting is 'new house smell'... concrete DOES smell. and it can for a year or three...so, oddly enough, does drywall. and spackle. and paint.

once you've eliminated the hazards- I've found that the easiest way to deal with it is a few cotton balls soaked with vanilla extract and/or clove oil...I jsut toss them into corners, but you can put them on little plates (or in the cap from a snapple bottle, which is largish and flat) and see if that helps.