I Cut My Thumb Pretty Deep With A Circular Saw

I cut my thumb pretty deep with a circular saw on the 3rd oof this month recieved stitches had them removed at prescribed time took some antibiotics cause of infection everything was good till today and then my thumb started to swell up my joint in my thumb has severe pain there is swelling heat and redness also why would my joint hurt and it uhurts to even touch anything with the pad of my thumb