I left my car for 4 weeks over the winter (freezing conditions, etc.)

When I returned, there was a slight rubbing when using the brake that coud be felt through the pedal - almost like there was something stuck on the pad causing it to catch then work properly (much like on a bicycle when the rim is out of alignent). I tried braking hard a few times then normally and it seemed to subside. However, it's still there 3 months later. Brakes seem to work fine, I was wondering whether it could be a rust patch or maybe the pad was worn in one area or perhaps wheel balancing?