I changed out the front brake pads on my 97 Altima.  I have done this
several times in the past with no problems.

I had to force the piston back to allow the caliper to fit over the new
pads.  I have done this the same way in the past.

Now, the brake pedal is very spongy, and the fluid reservoir is over-full.
Did I force the fluid backwards into the reservoir?   I don't think any air
was introduced into the system (it couldn't have, really).

Is it possible that over time, things will work themselves out right where
they were before or do I have to do something to correct this?