Caterpillar poop or something else?

You could try and remove the parts affected..........or just leave it and deal with it at harvest. Caterpillars (little black crumbs are their poop and a give away sign to their presence) can bore into the buds and cause damge, but they generally don't cause bud rot, which is something else all together. It does not look like you have bud rot, just a plant pest. Bud rot will be all mushy inside the flowers and usually the first sign of it is many dead leaves around the affected bud. I would not spray anything onto the plant this close to harvest..............no matter how safe it claims to be. Removal of affected parts may be the safest solution regardless of the cause.

thats rotting. either from insect debris or some other reason. I would chop immedeatly to at least get some out of it. Washing buds is also possible,

inspect whole plant branch by branch, bud by bud and pull the buds out from the stems to inspect. look for signs such as webbing or what looks like little dog hairs stuck to your plant. our any leaves that are curled inwards in an unnatural way. chop what you have to. they will create mold and the mold will spread if not stopped. you could also spray some preventatives after wards such as an essential oil based bug spray but its not going to fix any issues already happening. some will use something heavier this late in flower. i dont personally like doing it but i have in the past. just keep a watchful eye for signs of them being around or on your plant. its hard to get them before they do damage unless you have a good IPM regiment

Looks like its full of insect poop and rotting, better cut that off and throw it away to be honest...