How To Treat Swelling And Discolouration Of Finger Caused Due To An Injury?

My husband smashed his finger at work. It instantly swelled and turned black and he was seen by a medic on site, so that meant he had to go to the hospital. He went and the doctor wanted xrays in the morning but due to his work schedule he was not able to and the emergency doctor said he should be fine. The blackness has went away but it is still swollen and numb. He had someone tell him that there could now be a blood clot floating around his body that he is worried about, so I am just wondering if he should go to the hospital for this?