That's not a waterpump light, it's a LOW COOLANT light.
Overfill the reservoir 1/2" above the FULL line.
Then, keep an eye on the level. If the level was low, it may take a while to make sure that all the air is out of the system.
If the level continues to drop, it will be necessary to pressure test the system to see if (and where) it's leaking. Most shops can do this if they have the proper tester cap for your car (ask first).
Steve