My 12 year old son is in puberty. He has quite a bit of pubic hair, under arm hair, acne and one nipple has enlarged and a lump behind it. His penis had enlarged quite a bit and testicles. However, over the past 6 weeks or so he has noticed about 1/2" in diameter hard lump under his left under arm. In the beginning it hurt, but said it doesn't now. The size has not gone down. I also feel another lump in the other underarm as well. Not as big though. Is this something we should be concerned about?