Not sure which part you mean is sticking.
But, again dont know how good your discs and pads are..
Lets go that discs and pads are good..
When you have your wheel off, your brake calliper lever, should go all the way to the stop, regardless ... IF, your hand brake cable is sticking inside, then every time you pull your hand brake on, the rear pads are locking to your disc.
But when you release your hand brake, because the inner cable/wire is sticking in the outer cable/ sheath, your calliper hand brake lever can not return, so your brake pads are sticking.
Now as you drive, your brake pads will wear away enough, that every time you touch the brake pedal, the adjuster inside the piston/ calliper, takes the free play up in the pads.
But the lever has not moved back to the stop, because of the cable..
This can go on for a few days/weeks, and the cable will be allowed to come out of the ADJUSTING bar in side your centre consul. As you will have pulled the cable that many times and worn your rear pads away.
So now ,,,, you need to work out is it your cable or calliper, but because you have made the calliper lever go further than it should, that will stick....
Disconnect your cable,,, pull the lever back to its stop.
Now with a pair of molegrips/pliars move the lever back and forth, until it feels ok. you will know when this is.
When you have done this, and your lever is on its stop,,,,, get in the car and pump your pedal,,,.
This will reset the inner worm gear and piston, back to where they will work.
Back under the car, get the lever, and when you force it forward, with your molegrips, the rear brake will lock, release the lever, if it comes back on its own, to the stop..
All is good.
So this now leaves the cable, replace the cable,,, nothing can be done with it, you will just waste your time.....