I froze my iMessage app by sending too large a message, what can I do?

About 40 minutes ago I froze my iMessage app by sending too large a message. It consisted of emoji's, copied and pasted until a huge message was created. Now, I'm unable to open iMessage without the app crashing after about 10-15 seconds. I've tried a standard reboot and the hard shut down type thing (where you hold the lock and home buttons until shutoff).It's still crashing though, what can I do?

(note: iPhone 4s, 32gb.)

Easy fix. Go to any contact on your phone and then click a "share" option. It should go to your messages app. Then, cancel that share. You should be in your messages app. Now, delete the conversation with the large message and you should be good.