I don't think I have gone through puberty. I'm 12 and I got a 1.3 on the test, but I get erections due to just reading about puberty. Can I get sexual arousing erections even though I haven't started puberty? Is that a sign of puberty?
The early signs of puberty in boys are usually subtle and easily overlooked. For example, one of the earliest signs is a swelling and reddening of the scrotum. Because it is a gradual change, most guys don't notice it. Erections where the penis swells is something that can't be easily ignored. Sometimes hair begins to show up near the base of the penis about the same time.
Thus, in answer to your question: You have started adolescence. You've started the journey to becoming a man.