Can't figure out why my finger hurts so bad - I didn't jam it. Any ideas?

Last week my left pointer finger started hurting a little bit, enough to notice but not enough to worry. I didn’t jam it or do anything that I can think of that would have made it start to hurt. Well, yesterday it was hurting pretty bad and when I woke up this morning the pain is excruciating. I can’t do anything with it – I’m currently typing with my middle finger on my left hand (which surprisingly isn’t so hard). Anyway, it is a little swollen but I cannot for the life of me figure out what could be wrong with it. It took me so long to change Meadow’s diaper and button her back up this morning. I’m definitely going to make an appointment this morning but what the heck could it be? Arthritis? I sure hope not!!!!!!