Possible broken pacman hind leg.

[BossFrog]

Hopefully it is just a sprain! It could definitely be worse! Can you post a picture? That would really help us help him.

[Bynny Ribbit]

You should probably take him to the vet. Has he been eating or doing any of his normal activities? With the way his leg is, it might interfere with is ability to burrow not to mention the pain may keep him from wanting to eat.

It could heal on its own, but not getting it checked out could be detrimental to his quality of life.

Also...

"Pet store says to soak him in the water dish to see if it's actually a shedding issue...Pet store says it'll fall off..."

Lmao, you tell the pet store his leg may be broken and they think it's a shedding issue? For the sake of your frog, please don't get advice from this pet store anymore because they obviously have no clue what they are talking about. The leg would only fall off if it was necrotizing, and at that point the frog would likely be difficult to save.