This is one of the most horrific situations one can encounter whilst at home. The first solution is using a toilet plunger to remove any visible blockage. If there isn’t any visibility and the water has come to the top remove some water if you can or prepare for some spillage.
If you have an industrial garage blockage remover use that with cold water and let it sit for 10 minutes before flushing.If unavailable use some vinegar and baking soda, this should create a chemical reaction that creates heat which shall hopefully remove the blockage and you will see the water level go down. If this is not the case try not to tamper any further and call an expert DASH plumber by simply visiting www.dashonduty.in/.