Help! my african dwarf frog is missing his hand :( will he be ok?

I just got two african dwarf frogs and one of them is missing his front hand. its just a nub. will he be ok??? he can swim to the top for air i have seen him do it.
Update: hes not with any fish, he was at the pet store, but i just have him with another african dwarf frog now. i heard you can get medicine to put in the water? should i do that? will his hand grow back like a lizards tail?
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