Summarize the following:
Swelling is one of the primary signs of a sprained finger. If your finger was bent uncomfortably far to one side or the other, the ligaments connected to the finger’s bones may be stretched or torn. The tendons will swell on the side opposite the way in which the finger was bent. So, if your finger was forced too far to the left, look for swelling on the right side of the finger. Notice if the soft underside of your finger seems puffier than usual. If so, this is a sign that the finger has been sprained and that the ligaments near the base of your finger have been stretched or torn. If you’re not sure whether or not the finger is swollen, compare it with the corresponding finger on your other hand. Along with swelling, the most notable sign of a sprained finger is red discoloration. Inspect the sides and bottom of your finger. If the finger is more red than the surrounding fingers, it’s likely sprained.  The degree of redness will vary with the severity of the sprain. So, if your finger is lightly sprained, the skin covering the sprained tendon may be slightly pink. If the sprain is severe, a large portion of the finger may be notably bright red.

Summary:
Look for swelling on the sides of your finger if it was bent sideways. Inspect the bottom of your finger if the finger was bent backwards. See if parts of your finger have turned a shade of red.