I apologize that no one has responded to your question sooner. Different experts come online at various times. I just came online and saw your question. My name is XXXXX XXXXX I'm a biologist with a special interest in reptiles. I'm sorry to hear of this incident.
If the small lizard was toxic, you would have seen effects by now, so the biggest danger is impaction. You can use a special soak as a first aid measure. Buy some Pedialyte (yes, the kind for human infants), and prepare a shallow warm bath consisting of 1/2 warm water and 1/2 Pedialyte. Soak your dragon for about 20 to 30 minutes. After the first 10 minutes, with him still in the water, gently massage his underside from front to vent (where droppings pass out) for an additional 10 minutes. That may be enough to help him pass some feces. Try to get him to swim while he's in the water, as that can help, too. Be sure to supervise closely. This can be repeated twice a day.
If your dragon loses his appetite, continues to be unable to poo after several soaks, or his abdomen swells, you'll need to see a reptile vet. This link will help you find one:
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