Can you give us a series of shots of the problem? Just the one doesn't give me the sense of scale I need, but that looks like rot and needs to be excised ASAP.

What happened to it? did it survive?....

Help! I'm new to this gardening thing, and was so excited when I got this a few weeks ago, but now it has these horrible brown spots with discolouration around them, and now I'm freaking out about the rot comment further up! Lol! Can this be fixed some how? Or is my little beauty headed for plant heaven :( ?

This is a slightly better pic (I think), oh and I forgot to mention it's only on one side of the plant, the other two are showing no signs of anything weird.

Is the spots smushy

If so it is for take the rot back scraping it to good tissue on the cactus when u get to tissue that ant mushy or soft stop put some good alcohol on the spots with a qtip and let it dry repeat the applying of alcohol two to three times then the spots should scan up for u in a few days stop watering it for about 4 weeks and then put ur finger down in the pot on the edge to see if it is still damp if so don't water till it is dryed out completely then only water a bit hope this helps if its not to late