What is this?
 

Went to change my oil today and noticed this while I was under the car, it was right behind the oil pan.

That looks like someone used a cheating method to access one of the last bolts for the oil pan for a leaking oil pan gasket. But, that is just a guess. I bet if you look behind that bolt, it will be one of the bolts for the oil pan.

So is this something I need to worry about?

you should question the person you bought the car from, find out where the oil pan gasket was changed, and then challenge the shop on their work. Unless you just had the oil pan gasket done.

Drilling the hole through the transfer case is something that saves many hours of work, and is a MAJOR shortcut for the oil pan gasket job. If you saved money by that method, then you have to assume the riskk of the transfer case failing.
If you paid full price for the work, then you need to confront them. and have them Assume the risk of a TC failure.

certainly this conversation would be easier if you were to write some more details.

I have only had the car about 4 months, that is the first time I have been under it. It is no longer covered by a dealer warranty so I doubt he would care about it.

The point is that somebody paid 10 hours labour to change the gasket ... and they only did a 3 hour job. In the process they have compromised the structure of an already weak component of the car.

On top of that, the technicians here get FIRED on the spot for doing something llike that.
The dealer had better care, if they dont, you need to bring this substandard work to the attention of the better business bureau.

maybe the dealer didnt do it, probably whoever had the car before it went to the dealer. i did this to my x last winter, put 11 thousand mi on it and only problem ive had is no more oil spots on garage floor. saved like a grand in labor too. -stevis05