What Causes Swollen Knuckle?

hi, i am a 24 yr old male pretty fit and healthy. 1 week ago a thin peice of metal entered my pinky finger at work just below the knuckle and went in pretty deep about 2 or 3 cm up my finger towards the knuckle. the next day that half of my hand was swollen and really painfull so i went to the hospital and was put on antibiodics. the pain has mainly gone ecxept for the knuckle but its still just as swollen as it was b4 the antibiodics. could it just be fluid in my hand thats causing swelling because the pain is gone so i am hoping its not infected still. thanx