How do I re-insert a chain pin that has been pushed completely out? While breaking the chain, I pushed the pin too far and pushed it out completely. Now the chain is too short. How do I re-insert this pin, or should I look for other options.
What type of chain - Shimano have chain connector pins for exactly this task for many of their chains. Note the pin must exactly match the chain.  If you have a length of the same chain (I always keep the left overs when I put ion a new chain) break the chain again and remake the chain with the leftovers.

I have (in desperation - bike shops 100km away, no spare chain parts), used a vice and pointy grips to do press the pin in - the repair was dodgy but got us on the road. 

Alternately, use a quick link or a new chain.