my hubby has a rash

My husband works in construction and was in a manhole when a pipe broke further up the line and sent water puring onto him from a pipe about 10 feet up. This water was water that was sitting stagnant from sink drains. Not toilets. He swallowed a bunch of it in the process of trying not to drown! That was about a week or two ago. He now has a little patch on his back, larger than a 1/2 dollar. It is bumpy and itchy, but his new complaint is that it is painful. He had trouble sleeping on it last night. At first it looked like a little patch of yeast, so I put some nistatin on it. When that didn't work, I thought maybe it could be a poison ivy or something itchy. I tried some stuff for poison ivy/oak. That helped with the itch. But he said today, that he can feel it from back to front, internally. If that makes sense. It is on his mid back,  left side and he can locate the rash from his front side because of the discomfort. I do not know if this is linked to getting something from the nasty water he swallowed or something different. Any help? I thought about trying to put some tea tree oil on it, cuz its an analgesic, antiseptic and it would dry it up.... Just not sure what to do. Trying to save a trip to the doctor and a day off work.

[jagesh50]

Herpes zoster from your history is my clinical impression.He may break a rash sooner or later if i am  not wrong..Best seen early and treated by a doctor.

[32momof2]

Already looked into shingles. He does not have any blisters or "bubbles". It also does not seem to be spreading. Any other suggestions?