Hi Icunning,
Welcome to Apple Support Communities. We understand that you're having an issue with sending iMessages with dictation on your iPhone. We'd like to help.
Have you tried to force close the app and restart your iPhone. It is a simple step but it can sometimes resolve issues like the one you're having. If an app on your Mac stops responding, closes unexpectedly, or won’t open - Apple Support
Then, see if that made any changes to your Messages. If it didn't, you'll want to try to isolate this issue a bit more. Do you see that this happens in other apps as well? If so, which apps do you see it in?
Let us know and we'll continue from there.
Take care!