Two year old a bit too obsessed with his penis. What should I do?

My kiddo turned two last month.He's been interested in his penis since ~5 months old. Every time his diaper was off, he'd be touching/slapping/tugging on it. I thought nothing of it, as it only happened during diaper changes and baths.We're potty training right now, and most of the time when he's home he goes bottomless because he can't quite get his undies off by himself. He's ALWAYS touching it now. Mostly if I see it, I will just say "Touch your penis when you are alone, not in front of mama" and he'll reply "okay mama" but it only seems to be getting worse.I caught him yesterday with a little erection pressing it against the dishwasher, and today he was trying to press it against my leg.I guess the simple answer would be to just put undies on him more often, but he has more accidents in undies than he does when his bottom is bare. Is there anything else I can do to mitigate this behavior without making him feel ashamed?Thanks in advance! via /r/Parenting http://ift.tt/2yd8WIw