Just like in the original, the sequel, Hollow Knight: Silksong, also allows you to upgrade the Needle to hit hard and defeat the bugs at a faster rate than before. But it does take a while before this option unlocks for you. If you are struggling with one of the several difficult bosses and looking for when you can upgrade the damage on Needle, we have got you covered here.
How to Increase Weapon Damage in Hollow Knight: Silksong

You can upgrade your Needle at Pinmaster Plinney in the Bellhart area in Hollow Knight: Silksong. You will get access to the Bellhart area after passing Shellwood before heading over to Greymoor.
Once you reach the Bellhart area, jump on the small platforms to get to the upper level. Now take the route right, jump over the bell, and you will then get to Pinmaster Plinney’s hut. He is the Needlesmith in the game, whose only job is to upgrade the Needle to the next level.
Requirement for Upgrade: After you defeat the Widow boss and save Bellhart, you can head to upgrade your Needle. If you haven’t freed Bellhart, then you will not have access to the Plinney Needlesmith in the game.
Head inside and talk to the Pinmaster. After exhausting all the dialogue, you will get the option to Sharpen Needle. Choose Yes to upgrade your Needle. You can then check the Needle in your inventory, and it will be titled as Sharpened Needle.
After the upgrade, the Needle will also be able to deal higher damage than before.
About Upgrading the Needle:
The very first upgrade you will receive from the Pinmaster will be free of charge. Think of it as a reward for liberating the town; the next line of upgrades will require you to complete various quests for Pinmaster.
While you can certainly play the game without upgrading the Needle as part of a challenge run, having the Sharpen Needle will help you make the game a bit easier, especially if you are struggling to defeat bosses such as Sister Splinter or Moorwing in Hollow Knight: Silksong.