A tap-like sign with the word CHECK shows red on my dashboard. can u please explain?

Generally red sign are urgent! As for your description, I cant make out what you could possible mean by tap-like?? Maybe a picture could help??

I think water in radiator is low

The model of your car would have helped narrow it down.
If you have a red check sign come on, something needs immediate attention
Check/change oil+filter, coolants and other fluids.

My car model is Honda Bulldog

Top up the water level in your radiator!!!

The sign look more or less like a container cover

the sign means that something somewhere is faulty in your car, could be that ur injector nozzles are dirty, fuel filter is blocked, fuel strainer is dirty , could be a minor or major fault
u need to do a thorough check on your car to find out what is wrong

alternatively you could do an engine diagnostic test which will pin point what is wrong with car. after u fix it up, the diagnostic tool can be used to reset the memory of the car and the sign would clear out,

its a simple problem.
1. Your car could be using leaded fuel as against unleaded fuel specified for the car by its manufactorer
2. Your oxygen sensor in either of exhaust pot 1, pot 2 or manifold could have gone bad, its commonly called
indomie by local meachanics.
3. it could men that the emmission level of your car is not as it should be, meaning its emmitting more
CO₂ than specified by manufacture as against standard in certain countries. cos nowadays most
cars are to meet ULEV (ultra low emmission vehicle) standard.
In naija, this shouldnt bother u, as its no problem at all, keep driving ur car. But once u see the maintanance light lit, then u have to see a mechanic.

Alternatively, take your car to adigital diagnostic centre, it shouldnt cost more than 5k just to diagnose, but of u ask my opinion, its a waste of money.