If he just stepped in it, he'll be okay, just clean him up. What you need to worry about is if he ate it, or licked at it. If he consumed any, he'll probably get pretty sick. Similar to food poisoning, he'll be throwing up and going to the bathroom constantly until it all gets out of his system. You can check with the vet to see if they can prescribe anything to make it easier on him.
If this just happened, you'll see symptoms within a few hours. If nothing happens, he's fine.

