Should the one side of my gum still be sore and purple after a root canal and porcelain crown? (Photo)

I recently broke my tooth so the dentist performed a root canal and gave me a porcelain crown. It’s been a month and the one side of my gum is a dark purple and still sore constantly. He said it’s cause it’s not properly cleaned. Yet when I clean it, after, when I sleep, eat, etc there’s pain. I’m more than sure something was done wrong or is wrong due to not only the color but constant pain.