You should contact the seller immediately and explain what you did, although you should have asked before bidding,ask if the seller would be willing to ship to you in Canada if you win the auction. If he is unwilling to ship to you,ask if he could cancel your bid after apologizing for making without checking if the seller ships to your location.
You could also retract your bid. Although retracting a bid made by mistake is not a valid reason for a bid retraction,it's better than risking an unpaid item dispute if the seller won't let you off the hook if you win the auction,
Here is the bid retraction process.
Here's eBay's invalid bid retraction policy.
