Yikes!

And Jeremiah the prophet said to the prophet Hananiah, "Listen, Hananiah, the LORD has not sent you, and you have made this people trust in a lie. Therefore thus says the LORD: 'Behold, I will remove you from the face of the earth. This year you shall die, because you have uttered rebellion against the LORD.'"
In that same year, in the seventh month, the prophet Hananiah died.
Jeremiah 28:15-17

The penalty for false prophecy was death. And in this episode God dramatically rendered the sentence upon Hananiah in order to vindicate His message through Jeremiah. Hananiah pulled the wooden yoke off of Jeremiah's neck in disdain and boldly declared in God's name that within two years Babylon would fall and the exiles would be back home. He was denouncing the judgment that God had declared.

God quickly dealt with this prophetic rebellion. Jeremiah reaffirmed God's original message. God declared Hananiah in rebellion as a false prophet. Instead of the captives being released in two years, Hananiah would be dead in less than a year. And that is exactly what happened.

God can handle Himself nicely. The truth will triumph in Him. We need not worry about it. And circumstances will show the sovereign work of God's control. His Word will not fail and no rebellion among men will go unresolved. He will bring it all to the praise of His glory.