Lavender can be helpful for stings. I use the oil, but the plant works better if you don't have good quality oils; just crush some leaves and press them to the sting.

Other good candidates are peppermint and wintergreen, and don't be afraid to mix them!

You might also try oregano, but be careful with this one as the oil is quite strong and can burn sensitive skin unless diluted in a carrier oil like coconut, olive, or butter.