First of all, I call bullshit on "bound to get hurt." Yes, it's dumb and unnecessary for a beginner to be doing sets of 12 deadlifts, but you're never bound to get hurt unless you're a competitive athlete training with 110% intensity because your career is on the line.
Secondly, there's absolutely no such thing as a not serious lower back injury, especially when it comes to a teenager. The low back is notorious for repeat problems down the line if something goes wrong. If it was serious enough to stop you from lifting for a few weeks, then it's fucking serious.
Take a step back and try to see the long-term picture. If you can build some basic strength, size, and conditioning while staying healthy now, you set yourself up for huge gains in the next few years. Of if you keep doing what you've been doing, you can keep tweaking your back and needing time off, and never really get a great start.
It's totally your choice, but you're getting some solid info from more experienced people who are saying things you just don't want to hear.