You's have nothing to worry about at all.
If it was a problem then all these threads that are about this water sound would have an outcome with something like "it's this part" or you need to get this checked.
Ive had my MCS
for 2 year and 2 month and its been there since day 1.
Its not a problem and your car will be fine.
If you had a dodgy cylinder head then you would no about that from the way the car drives.
if you water temp needle does not go above the center line then the temp off the car is fine and running normal.
Just do you normal checks that every driver should do which is oil and cooland levels etc etc and if everything is ok then you have nothing to worry about.
Even if your coolant is slightly low then its not unusual for a car to be low sometimes its when i drastcially gets low quickly that you will have a problem.