When your dog slammed into you, this probably resulted in the collection of blood in that one spot. This generally leads to a discoloration. A swelling is also observed and you may find it slightly painful. This may be hematoma. If you find that you are unable to move your lower leg or that you feel that something is broken inside, then you should visit a doctor since this kind of an injury could well lead to an infection.
What you can do is to give your lower leg the heat treatment. You can use a heating pad. Or if you don't have that heat a folded towel on a hot pan and apply this to the affected area. You can repeat this several times. After this you can dip the towel in a bowl of cold water and apply this on the injured area. You may have to do this for a few times before you observe that there is a reduction in the swelling. You can also massage the area. However, remember to do this gently. Using some warm oil helps in lubricating the area and making it easier to massage. Your diet should be augmented with extra proteins to ensure complete recovery from the injury.
answered by G R