Basketball Injury To Foot

I was recently playing basketball in school and as I chased a ball going out I heavily planted my left foot onto the hardboard court. As soon as I did this I felt a shooting pain on the inside of my foot.
I thought nothing of it, thinking i had something in my shoe (there wasnt), and continued playing. I also attended rugby training the same night.
The following night I felt a light but constant sting in my left foot (inside just bellow the ankle but above the sole, same as basketball) so thought I'd have a look.
There is a lump of swelling where the pain is which isnt on the other foot. The pain is increasing and i would like some advice as to whats wrong and treatment.

I'd appreciate the help a.s.a.p as I've an up and coming prom that I'd like to walk into.

[Yena H Do, DPM]

sounds like you sprained a ligament.
apply an ace bandage daily.  i recommend icing for 20 minutes daily, and taking 600 mg ibuprofen every 6 hours for 5 days.  if the pain doesn't subside or worsens, go get an xray to rule out fractures.