I Cut My Knuckle On My Forefinger On My Left

I cut my knuckle on my forefinger on my left hand after managing to run into a door. The skin split open on the metal bit of the door jamb in the door frame. I wrapped it in a band aid and it healed with just a bit of bruising. It's about a month to 6 weeks later now, and now there's a strange bump under the scar. It hurts to put pressure on it, but otherwise it's fine. I'm thinking it's just a blood clot. Any ideas?