I love wasps, hornets, yellowjackets, etc., but I've been stung numerous times as well. Got stung by three of them this summer trying to move their nest from our porch without harming them, and my hand swelled up so much that I couldn't move my fingers.
The only advice I have is to put ice on it, it won't do anything to heal it, but it'll blunt the pain, if it's bad.