Does anyone recognise what this is? I've tried Dr Google but am having no luck.
I picked up 14-month-old DS out of his high chair this evening in the usual way by lifting from under his armpits. Immediately he twisted and tensed up the right side of his body and cried out. He was then very whimpery and hesitant to let go of me when I tried to sit him on the floor. I observed him crawling around for a while then and he did seem to be kind of 'limping' a bit, in the crawling sense (if that makes any sense!).
He did the same twist and cry thing when lifting him in and out of the bath. On the changing table afterwards, he was doing his usual trick of trying to roll to the left so he could sit up but he wasn't able to roll properly at all. 
Nursery said he was quite subdued and tearful at times today but I put that down to teething (he's cutting a molar). He seemed to brighten up a bit at home but was still quite subdued.
I'll take him to the GP tomorrow if he's no better in the morning, but in the meantime I have all sorts of worries running round my head. I've checked him over and there's no signs of bruising or anything anywhere. Could it just be a pulled muscle or something like that? A hernia even?