Without a plunger, the priority is preventing an overflow and giving a soft clog time to break down. Do not turn a simple blockage into a hazardous chemical mixture.
Stop the refill if the bowl is rising
Remove the tank lid and close the flapper if water is still entering, or shut off the supply valve. Do not flush again until the bowl level has clearly dropped.
Try hot, not boiling, water
For paper and organic waste, add a little dish soap followed by hot tap water. Boiling water can crack porcelain or damage components.
Give it time before trying again
Wait 15 to 30 minutes and watch whether the level falls. If it improves, a controlled test with a small amount of water checks the drain without filling the bowl all at once.
Solid objects need a different approach
Toys, wipes, sanitary products, and dropped objects do not dissolve. If you cannot retrieve the item from the bowl without pushing it deeper, use a toilet auger or call a plumber.