sounds like yellow jackets. Were any of the that stung you still stuck to your skin or did you have to pull or scrape any stingers out? If so they would be honey bees. If not or if any of them stung more than once,they are probably yellow yackets. You would have to find the entrance. You can usualy do this by approaching the area slowly while looking for bees going in and out. Once you find and mark the entrance you can go back at night and stick a hose in the hole and let it run for 20 minutes or so and that should take care of them without using any chemical methods.