What Are The Side Effects Expired Paracetamol Intake In A Child?

I just realised I've been feeding my 6 year old expired paracetamol solution!! It expired in December 2012! I opened it recently. Didn't realise it'd been in the cupboard for so long before I opened it as I always like to buy extra when I go to the shop, just in case. Now what do I do? He's taken it 3 times today and doesn't seem to be sick from it. I have binned the bottle and bought a new one, but I'm now worried.