Why won't DS (12mo) use his right arm??

[runnervt]

Hi

Since getting up from his nap ds won't use his right arm. It's limiting his crawling to a bum shuffle. He does move the arm but when h tries to pick things up it's with a very weak grip. It does seem to be sore when he tries to use it but not at other times. He's not himself at the moment anyway because of a cold but I can't see how that could be related.
Going to the doc later but any ideas while I wait??
Have read about pulled arm but I can't think of anything that could have happened to cause that.
TIA

has he slept on that arm? know i get da arm with pins an needles if i sleep on my arm

My ds was like this when he broke his arm (greenstick fracture).
Healed really quickly.

Sorry, was out at the GP who didn't seem too worried and said that if it was still the same to go to A&E tomorrow.
I still think he's done something to it. He was asleep in his buggy so I don't think he could have been lying on it. He's still not using it. I think it might be his wrist that hurts.
I'm expecting to go to A&E tomorrow and am now starting to worry I should have gone today instead. Would they want to x-ray it? How would they manage that??
Thanks