Spot on upper arm

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I have woken up this morning with a red spot on my upper arm which is very painful can someone advise please what mind of spot this is

It looks like a small infection, probably in a hair root. Keep it clean and it may come to a head and then disperse. Or it could just disappear.
If it gets very big or you feel unwell or you have redness that tracks away from the spot then see a doctor as soon as you can.