What Causes Pain And Tingling Sensation In The Arm After Injury?

Husband was trimming trees in Arizona 2 days ago. While he was picking up branches his middle finger hurt almost as if electrocuted. It immediately gave out. His first thought was torn tendon. Later he thought maybe scorpion. That night his right arm was feeling tingly and pain. Pain increases while lying down. The only way he slept was when his arm dangles down low but pain kept him up most of the night. Once he get up and moves it mostly goes away unless he s driving or doing something where his hands are above his heart like looking at phone. Once his hands are up the pain and tingling come. It s now the third night and it s still bothering him. I m concerned about why it involves whether his hand are above his heart level. Is this a weird sign of heart attack or just his body processing a possible scorpion sting?