Is it okay for a 15 year old to take protein shakes

Hello, I'm 15 years old and I training for boxing 3 times a week and I go to the gym usually every other unless I take a day off, I lift every time I go to the gym (usually low weight, high reps) as I am 5'7-5'8 and don't want to put lots of pressure on my spine. The other day bought two packets of optimum nutrition casein protein that I can take before going to bed when I get hungry instead of eating, it says on the back its for people aged over 18 years but I looked it up and some sites said that's it's fine to use as a teen, then other sights are saying its not and one even said it could effect my growth, what do you guys think? I have began taking it yet I just want to make sure if it's okay for me or if it's not. Thanks