I just played Mow the Lawn 2 and got stung multiple times by hornets from a nest in the ground.
Going to the hardware store for spray and then I'll play "Kill them ALL!. 
Had a yellowjacket nest in the yard and much like you, I found it the hard way. After parking a running lawn mower over it for a few minutes, I took it away and filled the hole with some fuel, twisted some newspaper into a wick, lit it, and stuffed the burning wick into the hole.
Homeboy here just screwed up as I basically capped the now fuel and fuel vapor filled nest hole with something burning = blammo! Now, I've got angry, burning yellowjackets on me as well as a burning newspaper wad as the exploding vapor pushed everything out in a very excited fashion.
Lesson learned. Now, I just nuke holes with chemicals from a distance.