you will need to see your medical provider so you can have your hand/fingers properly examined. it would not be possible to determine the reason(s) for your swelling over the internet since the exact details of your fractures is not known.
sprained two fingers fractured the bones used a splint for 4 weeks now both fingers are swollen and stiff. fell on my right hand and bent two fingers back waited two weeks and then went in for an x-ray that showed both fingers were fractured wore a buddy wrap splint for a month. now the splint has been off for a week and both fingers are still very swollen and stiff.