Christ's sacrifice covers sin, or atones for sin.
So there is no sin that God cannot remove... today.
What did God say...
Isaiah 1:18
“Come, now, and let us set matters straight between us,” says Jehovah. “Though your sins are like scarlet, They will be made as white as snow; Though they are as red as crimson cloth, They will become like wool.
Psalms 103:12-14
12 As far off as the sunrise is from the sunset, So far off from us he has put our transgressions. 13 As a father shows mercy to his sons, Jehovah has shown mercy to those who fear him. 14 For he well knows how we are formed, Remembering that we are dust.
Isaiah 43:25
I, I am the One who is blotting out your transgressions for my own sake, And I will not remember your sins.
So, when you say, "if I have sinned and that sin has not been removed", do you mean, if the person is not repentant - that is, is not sorry, remorseful, etc.?