Thank you for your email, and sorry to hear about your injury. Pinkies are very often injured in ball games. Besides being swollen and painful, is there a deformity? Or you are unable to extend the finger tip straight like before? There can be several common injuries, including a fracture. Another common injury is a mallet finger - either a soft tissue mallet, or a bony mallet injry where there is a little avulsion fracture. My advice is to see an orthopaedic surgeron, and get an X-ray done. That is the sure way to exclude a fracture.
Sometimes other investigations such as an MRI may also be warranted, if we are worried about capsular/ ligamentous or tendinous injuries as well. Another reason for an X-ray is also, should there be a fracture, you would want to get it treated asap, as a delay may result in poor/ delayed healing, or an abnormal/ displaced fracture. And if the X-rays do not show any fracture, you would at least have some peace of mind, and the proper management can be instituted for the injury.
Hope this helps,
Kind regards
Dr Sean Ng