There's no toxin in the bristles, it's just calcium, but it breaks off in the skin and is an irritant. (And a painful one!)
In the future, when stung hold your hand under as hot as water as you can stand, with the direction of the bristles going down. The water will release a lot of the bristles and your skin will loosen and help the bristles slide out.
It will make you a lot more miserable if you touch it!
If the hot water does not release all the bristles, soaking in vinegar will get any that are driven deeply into the skin. Once they are completely under the skin, you just have to wait it out -- usually a day or so before your body takes care of it. Usually it doesn't get that bad though.