Arshdeepji
Sin is a very Abrahamic word, it is something one does that makes God angry and that one has to ask God for forgiveness for. Similarly a good deed is something that makes God happy and reserves your place in heaven.
This is not how it works in Sikhism, in my opinion anyway, one does good deeds because one is a Sikh, our job is to serve and protect, not to get into heaven, but because it is the right and true thing to do, yes, we all do things we should not, but I do not class such as sins merely deeds that are not good.
If I were to walk past a woman being raped, that is not so good, if I were to join in, that is really not good, if I were to beat the rapist off and comfort the woman and call the police, that is good,
Sometimes it is hard to know what good is, and what bad is, is it good to give money to a beggar, knowing he may spend it on drugs? Is it wrong to do a good deed for the sole purpose of recounting it later to show others how good you wish to be seen as?
That is why we live by the truth, because where the truth is concerned there is no good or bad deeds, no sin, just the truth.
In our hearts, and through the shabad Guru, we find what the truth is, and we do our best to implement it in our day to day lives, sharing, helping, lifting the veil of darkness, that is our job, that to me is being a Sikh.