If my hernia repair (with mesh) isn't healing well, will I need another surgery?

Maybe. It is dependent on the type and location of the hernia, what type if mesh was used and the technique that was used to place it. It is also very dependent on what is meant by "not healing well". Stick with your surgeon, but if things don't seem to be progressing, feel free to get another opinion.
Perhaps. The two most common reasons for needing a second surgery after hernia repair is hernia recurrence or removal of infected mesh. If you are experiencing healing problems after hernia surgery, it is critical to return to see your hernia surgeon.