Lump on my dogs upper front leg?

My dog has suddenly developed an odd looking lump on the top of her front right leg. It's odd because it actually looks like a piece of sweetcorn stuck to her. However it is firmly attached to her leg and around the area it is very hard. It doesn't seem to bother her. I haven't seen her lick it or bite it or wine about it so Im not terribly worried. Just need to know if I should be. My dog is only two years old and she is a Labrador cocker spaniel cross and is considered a small dog.