That's one reason why I like to turn my newly gelded colts back out with a herd. That keeps them moving so that I don't have to LOL.
If he's had his tetanus shot, then you really shouldn't need to worry about that. Like Stevenson said, try not to get the wound itself wet. It will likely get crusty and look nasty, but leave it be. All that crust is protecting that new, raw flesh.
Also, fair warning. Some of the drainage might have the appearance of pus as it can become cloudy and thick. Don't let that freak you out. An easy way to tell if what you think is pus actually is or not is to smear some on your finger and smell it. Nasty, I know, but it works. Pus will smell nasty, but if the drainage is clean but cloudy, it won't have much of a smell at all.