Why won't hot water come out after turning the water main back on?
Since you have no water coming out or just a drip a large chunk of rust or scale could have broken loose from your main and plugged the water heater. I would close and open the valve to the water heater to see if this crumbles or breaks up the debris. If that works it really is time to flush the water heater from the bottom drain. A hose connected to the bottom drain and taken outside or to a close sink or toilet makes this job clean and easy. If you have valves on both the inlet and outlet cycle both. If this works on the outlet side be prepared to clean the faucet aerators. If you get water running and hot water again it is also time to check the Anode rod. Anodes reduce corrosion inside the water heater and are eaten away (Another source of gunk in the bottom of the tank). Good Luck.