2001 Nissan Sentra SE rear brakes

I did a brake job, like I've done a few times before, but this time I did something stupid and pushed the brakes when the caliper was off because I thought it was frozen. Well, needless to say, I pushed the piston all the way out, and got brake fluid everwhere. I managed to clean off the piston, and thread it back onto the rod inside the caliper, and turn it until it was in far enough to get the caliper over the new shoes and rotors. The problem is, now the pedal goes almost all the way to the floor before the brakes work. Is this just because I got a huge amount of air in the line? I filled the resevoir in the front, but it hasn't moved. The caliper doesn't seem to be leaking or anything. I haven't yet tried to bleed the brakes, because I can't do that alone. Is that the solution or is there other problems in play here?