You can see the ring is broken on the right side.
Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. It only takes a minute to sign up.Sign up to join this community
Yes - the rectangular hole on the right leads to a curved slot that holds the bolts used to secure your toilet. Your slot is broken which means the right side of the toilet will not be secure. This could (read will) lead to a rocking toilet (not in a good way) which will be followed by leaks (um, eww) and rotted subfloors or worse.
And I'd lean toward a stainless repair kit so there is less worry in the future.