I Have Had Swelling In My Armpits For 4 Days.

I have had swelling in my armpits for 4 days. First it was in my right armpit and now a similar lump is developing in my left armpit. I first noticed the pain after playing kickball 4 days ago but didn't notice the swelling until 2 days ago. They are painful and the larger one is about the size of a marble. I have never experienced swelling like this before. The one in my right armpit looks reddish. What might be the cause?