Tonight I noticed my dog start to limp. He won't walk on his right leg and he limps when walking. He's being very timid and not close to his usual playful self. Upon further examination of his leg my fiance noticed a scab. I then looked at the leg and felt something inside of the leg starting a little above the scab, it's separate from the bone but it runs almost in parallel with the bone and stops. Can you please help me in determining what this could be. I am very worried.