Should I do anything if I am cited for something that wasn't in my paper?
Since you never mention their technique, it is quite likely it's a "typo" (they accidentally cited a different paper than they meant, which, at least, in my field happens more than 0% of the time), or they just misunderstood your paper (or you misunderstood your paper).  I agree with @aeismail that there's nothing you need to do, but if you want to get to the bottom of this, you could contact the authors, saying something like:

I noticed you cited my paper in ... about X.  However, that paper didn't consider X.  Did you mean to refer to another paper?  If so, I'd be interested in knowing which paper.