Hi. My name is*****'m a camera repair technician with almost 30 years in the business and I'll be glad to help you with your question today.
This may be cured using the backfocus adjustment built into the camera. It's labelled AF Fine Tuning. There is a procedure to set this for every lens. Be sure you set this feature "ON" and leave it on, it's a great option for many back or forward focusing issues. Some camera shops will even offer this service for you. Also, make sure you are using a single point focus. If the problem turns out to be an issue with the lens itself, it's going to need to be calibrated by a qualified technician. You may want to check locally for a camera repair shop in your area, or, if you need assistance finding a shop, please let me know and I'll locate one for you.
Please provide a positive Rating so that I may be credited for my efforts. If I can be of further assistance, please ask rather than leave a negative response.