You see a baby rotworm.
The rotworm is harmless in this juvenile stadium. But take care to release it by time, otherwise it could get dangerous. At least it's your supplies being threatened instead of you.
Notes
It can be bought through the Store. It will be delivered to Your Store Inbox in a Decoration Kit.
When first used, it will go into the earth and stay there:
If used again, it will come back to its original state: