Hold down the power button of your MBA to shut it down and press it again to restart it and immediately afterwards hold down the Option/Alt key to get to the boot selector to select Mac OS X and press Enter.
After you successfully booted into Mac OS X, use the Boot Camp Assistant (BCA) to delete the Windows partition and quite the BCA. Start the BCA again and create a new Boot Camp partition and run the setup again, this time do not format the partition via the partition tools of the Windows installer, but when you get asked to either (Quick) Format it in either FAT32 (which it already is) or in NTFS.