Beats By Dr. Dre Right Earcup problem

Hey guys, so im kindoff new to toms, but i was wondering if you guys could help me with a problem with my beats by dr. dre. I bought them off a friend, and they worked great for two months, but all of a sudden, the sound in the right ear was significantly lower, almost to the point of no sound at all even though its hard to tell. Since i got it from my friend, its not under warranty any more, so im wondering if you guys either know a fix to the problem or a place that i could bring to fix them like best buy geek squad or something. thanks guys

P.S. sorry i didnt know what subcategory to put this under