Do you normally run your water heater on "Electric" or just propane? (Or both).
If propane, as stated above, just a reset and it will be ok.
If electric, you burned up your electric heating element.
Your water should have an electric on-off switch at the tank. As a double precaution, when there is no water in the tank, you should always flip that switch to off. Then, if the switch inside the camper gets bumped (like probably happened to you), the heat element will not come on.
So the thing you need to figure out first, was your heater on propane only, electric only, or both? Go from there.