What the fuck is this? Sudden pain!!

[Tictacbow]

Woke up and the inside of my left arm is in agony. Feels like I've burnt it but the skin isn't red or anything and I obviously haven't. Like a burn just beneath the skin. I haven't been lying on it and it doesn't hurt in a crampy way anyway. What on earth have I done?

No idea, but I'm so sorry for you!

I have had exactly what you describe in the same place for the last few week but on my dominant right arm.
Sudden onset, I think it woke me in the night in fact. Burning skin sensation rather than aching. No redness or rash.
I've kept an eye on it and I've noticed it's worse after repetitive movement such as vacuuming. I even noticed it worsen after a long drive so steering aggravated it.
After a consult with Dr Google , I've put it down to golfer's elbow but if it gets worse and more frequent I will see GP.
Let me know how you go, I'd be interested to see.

I have had the same on and off for months but on the tops of my thighs

Thanks it is still really painful today. Could be golfers elbow I hadn't thought of that.