I had a hernia surgery like 5 years ago but the doctor used mesh. Can I pierced my belly button?

Hello,
Thank you for your question. As Shakov explained, the navel piercing of the skin should be well-above the deeper layers of the abdominal wall. Like all piercings, abdominal piercings are at risk of infection, so it will be important to keep the area clean. If your surgery had been more recent, and your incision not yet healed, I would recommend waiting. 
Best wishes,
Dr. Moein

The mesh placed is deep at the level of the fascia or abdominal wall.  Above this layer is the subcutaneous fat, followed by the dermis and should not be affected by any piercings placed within the skin.