They are harmless but they will run away. You can find Moe-Eyes nearby, so don't worry about the poison.
On this island, you'll be tasked in finding moon shards. Once you reach the end, jump up to get on the slow moving platforms and duck under any more Bullet Bills until you reach the top of the tower where the checkpoint and Power Moon are at. Note that when you find a place to drop down and dodge the bullets, you can move left into a hidden area. Enter the 8-bit mural at the top of the tower and keep moving right while avoiding Bullet Bills.
