I've been in your shoes. I worked out when I was 14. Sporadically, but I did. Nutrition is really key here. You are going to keep growing, so if you ensure that you are eating correctly and remain moderatly active, its going to work itself out pretty easy.
Im not sure what your height is, but I dont know many 16 or 18 year old males that weigh in the 130s; its gonna change.