I put a wood clamp on a piece of stained wood yesterday and when I took the clamp off, it took some of the stain with it. When I tried to re-stain the wood, it did not seem to absorb the stain, even after some light sanding. This is leaving a slight mismatch in the color of the wood. Any ideas as to how to fix this problem? Thanks...

The clamp might have compressed the grains or had something oily in it.
Moisten the wood with a Q tip to raise the grain and let in more stain. Let it dry first and sand just slightly.