This trial tests a small device that sends electrical signals through tiny needles on the outer ear to help children with pain, post-concussion symptoms, and post-COVID-19 symptoms. The electrical signals aim to reduce pain and improve brain function by stimulating nerves in the ear. The use of electrical currents for the treatment of disease has been considered since antiquity but it has only been in recent years that suitable devices have been available to scientific investigators to provide stimulation currents for clinical use.