I never feed my buttons meal worms for this exact reason - I've never had it happen, but I've read that it can and so I never took the chance and fed them meal worms. So - do you feed them meal worms? If so, stop it! It might not be possible to make him stop thinking her toes are worms, but I'd say there is a reasonable chance if there are NEVER any actual worms around him. Eventually he should stop searching for them.
If you already got them into a habit of expecting worms from you, you could let your worms turn into beetles and feed them the beetles - they don't look like toes in any way. I gave a meal worm beetle to one of my buttons this morning for the first time and she loved it - wouldn't even share with her chicks ^^ But they are getting kind of big, guess she doesn't think they need her care anymore.
I agree with hughes that it might be necessary to separate them for a while - in particular if here are wounds on the hens feet now.