I have a son who is almost 3. He was a breast-fed baby and still puts his hands on my breasts occasionally and, i guess you could say, "rubs" them. (Like, when he is going to sleep) I think it is more of a comfort thing. I just dont react to it like it is a sexual thing. He will also lift my shirt so my belly is showing and put his bare belly to mine. The skin to skin contact is very comforting. He will do that and be asleep within 10 minutes. He also gets erections often. If you do not react to them they dont even notice. When you start making a big deal about these things is when they react in a negative way. You may also give them a sexual complex later in life if you teach them this is "bad" or "yucky". So, just remember, this is a natural thing. At this age they are learning more and more about themselves, their bodies, their surroundings, and the difference between boys and girls. Start teaching him now that "you cannot pull down mommy's pants." and the difference between boys and girls. (You DON'T have to go into detail about genitalia quite yet. lol) but you can incorporate this into daily things like in books, movies, and even at the store. as you see a girl, tell him it is a girl, same thing with boys...eventually he will be able to distinguish accordingly. I started with just people in the family. IE, "mommy is a girl, grandma is a girl, daddy is a boy, you are a boy" and so on. keep up the talks about what is appropriate and what is not when it comes to touching, dressing, and saying and he should be fine!!
Infants boys often have erections when breastfeeding.....
Anyway - normal, don't you be so weird about it:)
It's normal, a gently "lets get you clean", ignoring the erection would have been better unless you are trying to give him some very wierd hang ups and/or fetishes when he is older.