interject someone into something
to force someone into something, usually into someone else's business. I am going to have to interject Fred into this matter before it gets out of hand. I hate to interject myself into your affairs, but I have something to say.
interject something into something
to volunteer information or a comment into a conversation. We can always count on Liz to interject something sensible into our discussions. At last, something sensible has been interjected into our discussions.