Ink, like almost every Sans', is slightly chubby. He is also very short. (Just like his canon self, he is 3'8, making him one of the shortest Sans')
He doesn't mind being chubby, he doesn't really all that mind what his body looks like. The only thing he doesn't really like is the swirling patters of ink on his bones. The only two skeletons who know about the patterns are Dream and Blue. Even though Ink tries his best to hide the swirls of ink, he can't really hide them from his friends.
-Bean