My crown fell off last year, now my gum's swollen with a white bump on side of gums where the crown fell off. (Photo)

Hi:Please go to a dentist right away to evaluate the gum and the tooth without the crown.Best,Dr. Maddahi

It’s difficult to tell, but it may be an abscess. The tooth may be infected. Need to have that fixed (if possible), but you may end up loosing the molar. Either way, make an appointment to see a dentist ASAP before it gets worse.