Great responses. I recommend the following (I used to do this often):
Take any given passage that involves that "finger stuck" problem. Using the correct fingering as if you would normally play it (it would be helpful to write down the correct fingering if you are not comfortable remembering it), play those two notes (thumb and index finger) while also playing one (or two) note above and below those two note.
Slowly go up and down, up and down, gradually increasing tempo. Then, play staccato as Matthew Read suggested. Then, change the rhythm up. Then change the rhythm in a way where one (or more) notes are staccato, but one (or more) notes are non-staccato.
By "pushing" your fingers to do more, and to experience different positions, you will develop better control.
Really it comes down to what Widor said: practice. But yes, you must practice in a smart way (playing a short few notes in a variety of ways would be considered smart, IMO).
As a matter of fact, now that we are discussing this, I actually do this a LOT without even realizing it since I like to do a lot of improv. I'll be at my piano, and I'll find myself playing the same phrase multiple times in different ways <- usually when I'm just having fun and "messing" around.