People can try this:
1) Settings>Messages> Turn iMessage off
2) Use Siri to send a message to yourself and if possible the person who sent you the problematic text message
3) Settings>Messages> Turn iMessage on
4) Open Messages and delete the conversation that has the message in it.
5) If you still can't open Messages go to Settings>General>Reset>Reset Network Settings
6) Sign back into your Wifi Network
7) Try to open Messages again and it should work
If you can't get into your phone at all and it is stuck restarting you can use iTunes to restore a back up from before you got the message. If you have an iCloud back up you can use iCloud.com to erase your phone and then restore from an iCloud back up when you get the Hello screen. Since you would be erasing your phone you really want to make sure you have a back up before you do it.