There are multiple causes for something like this. The fact that is is ONLY one paw kind of indicates that there was or is something irritating that foot and causing her to lick it. Perhaps the groomers got too close with the clippers and got a little razor burn or maybe something unrelated to the grooming incident and she stepped on something, causing irritation... etc.

The problem is that... something irritates them, so they lick... then they keep licking and licking... and now they're causing irritation by the licking... which can lead to infection... and now they're licking because the skin is infected because of the licking... it can be a vicious cycle.

Because you're only noticing it on ONE foot, I would recommend a vet visit to rule out any other causes, like a foreign body, soft tissue damage, or just a secondary skin infection from all of the licking (but the primary cause is no longer a problem).