First, the crank arms are aluminum and the bb spindle is hardened steel. The crank arm is very unlikely to scratch the spindle. Second, a poorly fit crank arm will distort by having the square hole get too big, not too small.

Matt is correct in his suggestion though. Put the crank as far on the spindle as you can by hand then add the crank bolt and tighten it to about 25 to 30 foot-pounds. That should draw it down properly.