I've just been stung in the ear by a ground hornet. possibly multiple times. it hurts. what to do?

Simple treatment: When our bodies sustain an injury, the immediate response is inflammation (red, hot, tender swelling). This is the body increasing the blood flow to the injury to bring healing factors to the area and also the veins expand to carry bad stuff away. The key is to do things that reduce the parts of inflammation such as ice, compression, and anti-inflammatory medications in the first 24hrs.

Ground Hornet : (aka cicada killer wasp) tends not be very aggressive toward people. Wash area w soap ; warm water. Apply ice in 10 min. Increments (10 on/10 off). Can try tylenol, (acetaminophen) Aspirin or Motrin for pain or Benadryl for swelling. Elevate affected area for swelling. Make paste of 2 parts baking soda ; 1 part water ; apply. Need tetanus shot every 10 years. Throat, airway, mouth swelling or difficulty.