Fridge him. There's a sticky at the top of this forum about how to go about it.
An important thing: keep your aged, dechlorinated water for daily water changes in the fridge with him, so there isn't a temperature shock when it comes to changing the water.
The cool temperatures will slow his metabolism and relax him, making it easier to pass.
Is he eating? If he's eating, and you're feeding him earthworms, this'll help to keep things moving. If you fridge him, he won't be inclined to eat, but if you had a cooler area of the house where you could keep him in a smaller tub, under a towel so it's nice and dark and calming, you could try feeding him to help him pass it before resorting to putting him in the fridge.
Ultimately, if he can't pass it, you're going to need to take him to a vet to sort out the impaction. : (
Hopefully someone with more and actual experience will be around soon to post and help you out; I can only parrot the advice I've already read here, and advise you to look at the fridge guide. I do hope he gets better soon, poor little chap!