Definitely, get another battery tester for sure. The one you have is good for low voltage alerts but not so good at voltage testing.
The picture of the charger clearly shows an unbalanced battery.
I would try to discharge the battery (use it or put on charger for storage charge) and re charge and test again.
The question now is... is it the battery or charger that has the issue ?
Charge another battery and see what the charger tells you about cell conditions after that.
Does the second battery show the same unbalanced charge as the first ?This could indicate a fault with the charger if the readings are the same as the first.
If they differ and battery two has a balanced charge, then battery one is indeed in question.
Remember.... your looking for 4.20 volts on each cell. Anything else and your out of balance.
It will surly still work but is a clear indication of an issue with something. If nothing else, the battery life is most definitely reduced.