Don't try too hard, Heater plugs may get break. It is a common problem in 1.3 MJD engines.
Have seen couple of Swift, one Ritz and a Punto with head open because of Heater plug broken.
if it is still hard, just leave it, it will not cause any harm to engine, except check engine light on console.
I'm driving with one faulty glow plugs for more than 50K kms, not faced any issues so far. Glow plugs will use be useful only when staring the car, especially during cold climate. if the car starts normally, that is more than fine.