The black rat snake seems to be healing well. The infection between the two layers of skin seems to have cleared up. Also, the lump inside the internal skin seems to be drying from the inside. It's looser when I press on it.

Here is a before and after picture of the injured area:
March 23rd


March 31st


I still have not seen him tongue flicking. We offered him a live mouse, but he was not interested... yet. We'll wait for him to shed and offer food again.