My dog had twice gotten a grass seed embedded into the paw between her toes. Fortunately I noticed the little entrance hole and took her to the vet as she was licking it so much...a BIG grass seed popped out..and he said it could grown in there...so that may be another option. Do you take your dog to a field that has dry grass. The second time it happened I squeezed it like he had done and it popped out ...freaked me out as the seeds have those long "arms" (and I thought it was a bug at first) on them and I can only imagine how it must have felt. I now always check her toes when we go to that park..especially when it is dry.
Good luck..pls update so we know.