Invite him to drink

With your few gold coins, you buy a bottle of wine and invite him to drink.

You talk a bit more when he closes the store, and he brings two crystal cups to a small table.
The blacksmith points you at the wall behind him, to take the corkscrew and drink together after a good day of work.

It's time for your move.
You can take the corkscrew and pierce his skull.
Or you can just open the wine and start to talk.