Dead Bud

Yea I would cut it especially it the off but if the rest of plant leaves ok good then cut it out it spreads to the rest

Not might be, but it is bud rot !!! Huge problem. Dispose ASAP. put plastic bag on, cut and chuck to toilet. Rot spreads by spores, so infection is all around ...

Might be bud rot, best to remove it and inspect to confirm. when its outside of the tent cut it in half, bud rot will have a grey whispy fuzz if its mature and will make the bud a bit squishy as its decomposing it. The smell will be a bit sour and off, not unlike a mushroom but not the same, mushrooms are earthy and not sour. If it is bud rot you will want to keep your RH low. like you are already doing to help prevent the spores from germinating. if you see the grey fuzz it means it has spores active and if you have any fans in the tent its likely spread aorund. Bud washing with a peroxide rinse could help bring the number of active spores down but it also can zap away the terpenes. hopefully this is just a accidental branch snap and not bud rot. Good Luck!

And its important to being sure... When cut it take it in ur hands and close to nose. If it smell like some sort of mushroom - its make it nearly 100% confirmed its grey mold. Forgot to add to prev. answer.

There are some ways to try deal with it. Chemically (never used but u can try, the best would be to water with it. Hard to tell if it wouldnt harm so buds, during flowering its risky to treat buds directly by sprinkling chems) - preparations for strawberrys grey mold could be good. Its matters active substance which that prepation holds. Natural - garlic extract. U can get it in good gardener shop. Or make by yourself. Hope its not that