Hi, and thanks for your medical question on eHealth forum!
You probably mean that your testicle does not remain in the scrotum. This is a retractile testicle that moves to and fro between the inguinal canal and the scrotum. Usually this problem corrects by itself by puberty. An overactive cremaster muscle causes this. At your age, this can become an ascending testis and will no longer come back to scrotum after some time.
To bring the testis permanently to scrotum hormonal treatment is given and surgery (orchiopexy) is performed. If this is not treated, then later it may result in low sperm count and infertility. Please consult an urologist and get this evaluated. Hope this helps. Take care!