This brings me back to my Warcraft II days. Those exploding goblins sure are messy.
At first I thought it was a statuette in the shape of a goblin that was believed to bring fortune to its owner, which contained a hidden explosive material.
I don't see how they could mistake an anti-tank mine for a goblin. Do goblins actually exist in their folklore?
I think that it's more likely that the owner of the mine couldn't find a buyer, so he decided to get rid of it. Since there are probably no explosives experts in that village, he decided to ask the healer to do it, which led to that explosion. The whole goblin story was probably just a cover-up.