One of my grey tree frogs lost a toe pad, it healed on its own and although I know they don't regenerate, he did form a stubby faux toe pad. I do suggest switching to wet paper towels as a substrate (or putting your frog in a hospital tank of sorts) until the toe has healed to avoid infection. You can also keep it clean by misting with treated/filtered water.
Here's some pics of his toe now
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