A clogged toilet will usually unclog itself over time if you wait long enough. Most things that clog a toilet are water-soluble which means they will eventually dissolve in the toilet water.
The most important thing you can do in this situation is not to flush a second time. Forcing the toilet to flush again releases gallons of water into the toilet bowl and will cause an overflow.
Check water level in toilet bowl. Listen for a gurgling sound from the drain (a good sign) and check the water level in the toilet bowl. If nearly all the water drained from the bowl, then you’ve probably cleared the clog.
In case the matter is more serious plungers do not work anymore and at this point of time plumbers come up with a much stronger instrument known as the toilet auger or toilet snake.
The national average cost to unclog a toilet is $200 to $700, with most people spending about $350 for a plumber to use an electric auger to clear the toilet drain clog and test the system.