He has a child and I didn't know

I'm 17 and my boyfriend is 19 and I just found out that he has a child. We've only been going out a few months but I feel like telling someone you have a child should be said at the beginning of the relationship. I saw a picture of my boyfriend and his son on Instagram earlier today and I texted him and asked if it was a nephew or cousin but he said it was his son and he's 2 years old. I don't know what to do about the situation.