Wondering if it's normal to have pain 3 days after having a supernumerary tooth extracted?

Can be: There will be some pain or discomfort after this extraction and it will depend on the difficulty of the extraction, surgical or simple and your personal factors, health history and sensitivity to pain. Follow the instructions given at the time of the extraction. If you are having severe pain or swelling you should call the extracting dentist.

Surgery: You had surgery done. It's going to take time to heal. If tooth was impacted healing will take longer as surgery was more complex. Severe pain, swelling, bleeding, should be reported to treating dentist or specialist. If your not sure, call. Don't "tough it out" if you think there may be a problem. Call. Otherwise, follow the written post-treatment instructions that thou received.