ok what should i do? to trim the infected parts? or harvest as soon as possible?
As painful as it is, gotta cut it all out, and at least 3" either way. You could spray with peroxide, but that's a slippery slope, because you are adding moisture to a mess. Be careful when excising, use a closed container as spores are easily spread. We've all lost tops, nice buds this way. But you have to weigh the decision; am I going to lose more or less if I do (or dont) harvest. Me, once I start to chop the rot out, ill also get rid of some leaf for better air flow. This may stunt growth for a bit, but its better than losing a lady.
Peace