I had a similar incident, although not on a bike, I was on a ladder about 15' in the air and a bee flew out a small hole in my eves, flew right in my mouth and stung me in almost exactly the same place as I spit it out. Unfortunately I DID swell up and had a LOT of pain. I damn near fell off the ladder and caught myself on the way down, that was one of the diciest situations I have ever experienced.