Wobbly cranks/tightening with a household tool?

I'm not sure 'a little crash' would loosen your cranks Jack.
I would have a good investigate to make sure something hasn't bent.

WJPrince is right.
A crash would not unscrew a crank bolt. You might have stripped a thread or something else along these lines.
You should go down to your LBS and have them take the crank off to check for damage. Anything found now could well be cheaply repairable, ride around on it and you'll just compound the damage and could end up needing a new crank-set.
An LBS won't charge much more than a fiver to have a look - ask them first for a price.