Did you clean and inspect the pistons?
If you're fitting new pads, as they are thicker the pistons will now be pushed into the caliper a bit more than before, so your seals will be running on part of the piston that was previously exposed to the elements.
If it's scratch, corroded or dirty it will not move as smoothly on the seals. Typically, driving the piston back out a bit and going at them with an old tooth brush and brake cleaner will sort it out followed by a smear of red rubber grease.
....Else just run it as it is and the exercise and thermal cycling may free it up. :-)
Just be aware the danger is, if it binds and drags too much, two things: Heat will build in the disc and it'll probably warp it, as well as wear. OR heat builds up in the caliper, the brake fluid turns to steam and pushing the pad even more against the disc and when you do pull the lever it'll come all the way back to the bars with no effect.
Just make sure the discs arent getting stupidly hot during normal riding.