Okay...
About a month ago I noticed a small zit like bump on the penis shaft.
I had no clue what it was. However, I kind of figured it was only a zit. (Prolly a dumb thought)
So I proceeded to pop it like a zit. It popped, and then grew larger about a week after. I'm not sure what it is.
Then I was picking at it in the shower and it sort-of popped again... only this time, blood and zit stuff came out.
Any help?

Can be a zit, yes you get them there. Could be an ingrown hair, they are often a real issue there.

Either can be an issue, if they would get infected.

Of course they can be other things, are you sexually active ? Do you masterbate on a regular basis, do you do it rough sometimes ?

Most likely to be a zit, I know not of any diseases from sexual activity that cause zits, at any rate its most likely a zit in wich case you don't touch it, like a zit on your face.