Pins & Needles

Enii

You know when you lie on your arm and stop the blood and then when you move your arm you get "pins & needles". What is exactly happening here? And another thing, is it called pins & needles worldwide or do other countries have other names for it?

Beyond curious.

This has to do with the nerves as well as with the blood supply. Some people speak of an arm or a leg that is sleeping.
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DrIndy

Nerve compression causes this - commonly people lean on their radial or ulnar nerve which supply their arm and run under their upper arm or the leg is affected.

The feeling of cold is because the nerve starts working again.

There are compression points you can pinch to give a dead arm and its a cool trick to play on someone.

If you press for too long as someone is passed out, you can get drunken palsy and the nerve function can actually take some time to fully recover.