We recently had a similar problem on our club's portable layout which has cork roadbed over 2" pink foam. To solve the problem we loosened a few inches of the track, used longer sewing pins (1 1/2" or so) to push the track into alignment and then re-ballasted and re-glued the track. After the glue dried we pulled the pins. So far so good. We were replacing the ballast anyhow so the realignment was just part of the process.
We also learned a lesson about replacing ballast on modules that are assembled together. Don't! The glue seeped down between the modules and we had a heck of a time breaking them apart. Fortunately no damage was done.
I had a similar problem with a kink on a curve with foam road bed. Rather than tearing up the track, I fixed it by soldering heavy (14ish) gauge wire to the outside of both rails at the kink area. Then take the wire and lay it flat pointing in the direction that you want to pull the track, presumably towards the inside of the curve perpendicular to the rails. Note that the wire from the outside rail has to pass through or beneath the ties. Run it an inch or two away from the track. Then put a bend in it and use a sturdy glue (I used hot glue) to glue it down to the track.
Once the glue sets, the heavy wires are firmly tied to each rail and to the subroadbed. Then grip each of the two wires with needlenose pliers and twist, putting tension in them and pulling the track into proper alignment. The wires should be thick enough that the rails can't bend them back straight, but to be safe, you can glue down the wires in their twisted shape to ensure they stay that way. Bonus, you get a new pair of track feeders out of it!
I dunno if this would work for you, but it did for me, and it was much easier than relaying track.
Boy, lots of good advice...I think I will try the hon3critter fix followed by floridaflyer fix followed by tear up and replace.
Bear "It's all about having fun."
Model Railroader magazine