Most dogs have dew claws on their front legs, situated a little way up from the pad, to the back and inside of the leg, Some dogs also have rear dew claws, and some even have double dew claws on the hind legs which may require surgical removal, as they easily get caught in undergrowth and fur causing problems. Normal dew claws need to be checked regularly as they will grow at the same rate as the other claws, but have nothing to wear them down during exercise and therefore will need periodic trimming as they can grow round and back into the pad, causing pain, lameness and infection. If you are confident to trim them yourself, using a good pair of doggy nail trimmers, then take care not to cut them too short, as they can bleed. The alternative is to ask your vet or an experienced dog owner to do this for you.
… Anne
This happened recently to my Toby a Cavalier King Charles. His fur has grown long over the winter period to keep him warm (he is having a bath, cut, blow dry, nail clip next week) I did not realise that a dew claw had grown really long in a circular manner, and if left, would have embedded into his soft fleshy pad.
Fortunately my Sister Anne spotted it and we managed to trim it down: -- Toby is a very placid little man and absolutely adores me -- which is fortunate. He lets me do anything to him, including eye/ear drops, and teeth brushing services.