Does he lunge for a certain amount of time before he decides that it is a better idea to pin his ears and lunge himself towards you?
Next time you lunge him, pay careful attention to your signals, where you are standing, how you hold your whip, or even better if possible, have somebody video you lunging him, with both you and the pony in the video so we might be able to see if it is a handling error.
Have you had him for long? He might respect your dads size more than you, and if that happens to end up being the issue, you need to make yourself the biggest, scariest thing there, might look stupid but stand up tall, chin up, shoulders as broad as you can make them, chest puffed and arms wide, not tucked into your body, he needs to respect you, getting you in the nose with a hoof is definitely not allowed, you are very lucky he didn't do more damage than that.
However I think if possible a video of you lunging him would be the most beneficial, it's always hard to give advice if we don't know whether it is the pony being a flat out brat, or if perhaps your giving conflicting signals and that is his reaction to confusion. When does he pin his ears?
R.I.P ~ Bubbles - 25yo tb mare - 13.04.2011 ~ 8:30am ~ passed away naturally and peacefully in my arms