Once inattentive and it happened, you caused a short circuit, the Arduino does not run anymore, unless you plug the usb cable into the computer?
you have just successfully fried the onboard 5V voltage converter from the arduino 😀
Dirty workaround : connect a mobile phone power supply to the usb-port and simply continue using it.
But if you want to repair the whole thing, it is not difficult.
The part only costs about 10 to 20 Cent and can be replaced quickly, you only need some skills and a soldering iron.
What you need is an AMS1117-5V Voltage Regulator SMD
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