Forbidden pop!! Not sure what’s going on yet..

This started off as what seemed like a small pimple. Over the past couple days, it’s swollen up and my whole hand is swollen. In lots of pain all the way through my fingers and in my wrist. Went to the doc today and they gave me a Rocephin shot and oral doxycycline to take. I’m going back in the morning at 8 AM to get it checked again. They said to get to the ER if it swells beyond the lines.