So I was about to go down into the ruin to turn on the steam and what not, but after Neloth used the elevator, I left to go do some stuff before I followed him. Now a couple real days later I go back to actually do the quest and I am locked out. What do I do?

P.S. I can't revert to a previous save as the last save I could have used is a week gone by now.

Then you have to go waaay back. In the dungeon he will at one point give you the cube that lets you in and out. If you cannot get back in, there is nothing you can do unless someone on pc knows how. Sorry.

Actually, after waking up a little more a realized there is a skyrim wikia, so I went over there and found out that if you are at Nchardak, fast travel to raven rock, then fast travel back to the Nchardak, you can go in again. Thanks for the help tho Spread the word!

Great news. Thanks for the heads up. There are alot of people that have gotte stuck like that.