the line 222 refers to the error code in that file, not to the error. the problem is that your server is timing out before whatever is on that page can finish loading.
there is either some type of script posted to that topic or a link to another site that is not loading or an image that is not loading or something like that.
you do not need to know any kind of php to look for this.
if you have a recent database backup file from before this happened, you could restore that backup. you would lose any posts, etc. since that backup was made, but at least the board would work.
or , you can use phpmyadmin, go to the posts_text table, browse it.
there is no real easy way to do this.
you can try the toolkit and run the security scan to see if it picks it up.