The gums below my crown have changed; they now protrude out like a large bump? Is this anything to worry about? (Photos)

My crown is approx. 2 years old. I did not require a root canal. They do not hurt, are not sore at all...just hard. The opposite side of my mouth had the same procedure and the gums remain normal no protrusion. What would cause my gums to change like this...is it anything serious???