Whats wrong is my kitten?

well i have a cat whom had just borned with 3 kittens..and they were 3 months old...one of the kittens i realise it has this hump on the body where the umbilical cord was..its so red and quite big..i have thought of bringing it to the vet...but i wanted to confirm what was the hump first..its been there for around a month...pls help!?!?