This is a serious concern. If your water stays hot after flushing the cold tap a few minutes, turn off the source of power (and heat) to the hot water heater. Call a service repair representative for your brand of hot water tank.
If you don’t have a properly installed pressure relief valve, pressure can build in the tank. This is a potential threat to life and property and shouldn’t be ignored. Note that most recent hot water tank installations and replacements include the provision of a relief valve.
