I bit into something and my wisdom tooth broke but the root is still in my gums and it's painful. What should I do?

Please see your. dentist or oral surgeon. He/she will likely remove the root. Avoid pain and infection. Peace and good health. Modern dentistry is better than ever. You'll be glad you went.
Get help now. Important that you see Oral Surgeon ASAP. Root probably infected, and infection WILL spread. Once root removed make appointment with General Dentist for examination and cleaning. Important that you see Dentist regularly to make sure you don't have an acute problem again in the future.
See a dentist ASAP. You need to see a dentist or an oral surgeon right away to take out the rest of the wisdom tooth out before it gets infected and cause more problems.