You definitely don't want to use WD. It's designed to work its way down into all sorts of nooks and crannies. You may end up shorting something out and ruining your
mod. It's possible you just got some grit or a tiny bit of
juice down in there that's made the button sticky. You might try a bit of rubbing alcohol on an old toothbrush. Just gently scrub around the edges of the button, then let it sit for a few minutes to let the alcohol evaporate.
Also, if you have a can of duster (compressed air), you could do a couple sprays around the button, do the alcohol and toothbrush thing, then do a couple more sprays, and then let it sit for a few minutes.