Sticking caliper slide pins usually result in only the outboard pad being worn out. Don't be afraid to check them anyway...

But you should check the rubber brake hose for that side. It's possible the rubber collapsed inside the hose, acting sorta like a check valve. Then that side stays applied after you release the brake pedal.

Another thing might be the piston in that caliper is sticking. That would mean you need to rebuilt it (or buy a rebuilt caliper).