1920 One Cent Error - Advice?

Hello
My eight year old son and I are very new to this world of coin collecting, This weekend he bought a Canadian 1920 George Vth large one cent coin at the local flea market and then noticed that it appears to have an error. In the leaves around the outside there is a line from the end of one of the leaves to the vine.



Is this a die error? or something else? and if so is it rare? valuable? interesting? what do we do next? Please help a newbie ;-)

Thanks, Jim.