If you did not disturb anything else, that doesn't sound like the proper solution for the symptoms.
I would go back over the wiring to be sure you dont have a wire crossed or loose connections. If it all started with the amp's power cable being connected, be sure the cable isnt shorted. If your battery cable still gets hot, disconnect the amp cable and see if the battery cable returns to normal. Be absolutely sure all of your wires and cables have circuit protection, and that it's properly suited for each application and wire gauge.
In any case, I would not want to drive the car like this, or even leave the battery connected for any unsupervised period of time.