Do you know what caused the wound in the first place? Or did it just kind appear?
When you get your water stats, you should note that in freshwater mollies need very low nitrates compared to other fish, also check your pH, since corys and mollies have pretty much exact opposite preferences (though corys are more adaptable than mollies). Also, not really the issue here, but corys should be kept in groups

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How long have you had mollies in that tank?
The suggested bacterial medication should be tried before anything for parasites....
Some parasite medications could just worsen the situation

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