What is the ruling on the moisture that is inside the male organ and exits after urination?

What you see on the urethral opening after performing istinja' (washing after relieving oneself) is pure (tahir) and should be disregarded. As for the moisture present before removing the impurity (najasa), it is impure (najis) and must be removed. One must also beware of obsessive doubts (waswas) and not pay attention to them. If there is doubt about the nature of the moisture after istinja', the default principle is purity (tahara).