I over watered my cactus!? At least I judge that's the problem.. it is a tiny peruvian...

At least I judge that's the problem.. it is a tiny peruvian torch cutting (similar to San Pedro). It be fine, growing steady, but I repotted and watered and for the past week, it have been getting worse.

It looks resembling there is a "hole" or crack on one side, which is getting larger. It looks mushy, but the adjectives is small, so I don't want to touch it to make sure.

Anyway - how can I fix this? backing! Also what are the proper conditions for growing these cacti indoors?

Lighting: 250 Watt HPS
Humidity: 55%
Temp: 55-60F
What is the autograph of this baggy plant?
Answers:    Let it dry out it should pick up in a thaw but not sunny position.
Pool Crack Repair?
you have to stop hose and place it in dry place and every week you can hose for a smal amount only, don't place it within a direct sunlight, put it where surrounded by the morning it can get sunlight and bring back shade to when it is too hot...