Severed tree root
There is not much that can be done for roots damaged by digging. A minor amount of damage may have no visible effect but severe damage will cause branch dieback. The best help for root damaged trees is to prevent any additional stress. Keep the tree well watered during dry periods. Make sure mulch is not thicker than several inches and keep away from the trunk.
You also have the option of consulting with a certified arborist for an onsite diagnosis and the best way to proceed http://www.treesaregood.org/
Thank you. But as I explained it was 2" in diameter--kinda large. Should it be painted? And with what? (He was removing thick concrete with a hammer of all things!)
No, there is nothing else that you need to do. Painting of cuts is no longer recommended.