Can anyone throw any light on this?
Try #1472 and #1473 from the Catechism:
An example would be of a child breaking his parent’s window. The child can repent and be forgiven by his parents yet the window still remains broken after the parents forgive the child.
If you are worried about temporal punishment then please read about Divine Mercy Sunday: ewtn.com/Devotionals/mercy/feast.htm
Mortal sins are not forgiven during mass. If you are in a state of mortal sin then please get to the sacrament of reconcilliation as soon as possible and confess all mortal sins by kind and number so that the sacrament will be valid. As soon as possible though you should make an act of perfect contrition:
Remember, an act of perfect contrition must be said with the intent of receiving the Sacrament of Reconcilliation as soon as possible to be valid. Do not receive the Eucharist in the mean time though since you won’t know for sure whether or not your contrition was perfect.
Now, a question the original poster might be wondering is “Why go to confession when you haven’t committed any mortal sins?” Each Sacrament confers a grace:
When you receive the Sacrament of Reconcilliation not only are your sins forgiven but you are also strengthened to resist further sin:
Also, I reccomend the book “Swear to God” by Dr. Scott Hahn for learning more about the Sacraments.