You should definitely see a doctor
right away. Any time you scratch a part of your body, break the skin, and subsequently develop a swollen and discolored area around the scratch, it probably means you have an infection. Some infections of the soft tissue under the skin are not the big of a deal and they will heal on their own. Some are more serious and they need to be treated with antibiotics. Sometimes an infection creates an abscess
that needs surgically drained. Finally, rare infections can cause major tissue death that can result in a limb threatening (requiring amputation) or even life threatening disease. Thus, you should be seen today.
I suggest that you schedule an appointment with your primary care physician
today. If you cannot be seen by someone immediately, then I suggest that you go to the emergency room. A doctor needs to look at your foot and determine whether or not it represents a dangerous infection. If the infection looks dangerous, you may need admitted to the hospital for intravenous antibiotics. If your infection is not as serious, then you probably can get away with taking oral (pills) antibiotics. Either way, you should begin treatment immediately before the infection gets worse. Finally, you need to make sure that you are up to date on your tetanus shots.