Is this lump under my right nipple because of...(Please answer I'm concerned)?

Is this lump because I smoked weed, or am going through puberty? I know weed isn't bad but this has my attention. All in all, I've been high like only 14-22 times, and started smoking around October. I think it's called gynecomastia, and I read you can get it from excessive weed smoking. I smoked for the first time in about 3 months about 3-4 weeks ago, which was around the time I noticed this lump. I'm not sure when it came in, but I just happened to be squeezing my nipple one day and felt a lump. The more I squeezed it the bigger it got I think. I can't see it, but I can feel it for sure. I smoked a blunt with my friends, and like 3-4 days later did like 4 bowls over that weekend with my cousin. I don't know if that considered excessive smoking, but is that what caused it? I'm 17, nowhere near fat (121 pounds), about 5'6, my pit hairs have been coming in rapidly but they aren't really close to full grown (I can see a small patch in the mirror now and right side is longer than left), I can see my whiskers if I look close in the mirror, I'm getting chest and stomach hair, and my legs and arms were already a little hairy, but got hairier. I've been getting more facial acne than usual as well. I turn 18 in september. I haven't grown in like 3 years, and these are the first puberty signs I've witnessed since freshman year, excluding my beard which is like an inch if I make the hairs straight (been growing since last year). I think my penis grew from 5 to 6 inches over the past year, because it was 5 last year and about 6 now. I had the voice change later in 8th grade, and grew from 5'3 to 5'6 my freshman year. Can't remember when I got pubes, but I had them before high school for sure. It had o be 7th or 8th grade. lol size 9.5-10 shoe if it matters.