Honestly, it may never come back.
The entire key to hair re-growth in wounds lies with proper wound management immediately after the fact:
1) Of properly cleaning/dressing the wound immediately, so no tissue dies;
2) Of properly aligning the skin when stapling/stitching;
3) Of using a proper healing remedy, such as
Essential Wound Care, which keeps the tissue moist and promotes healing (esp. w/ Vitamin E).
If you did all of these things, then the chances for minimal scarring and hair re-growth are excellent. However, if you let the wound get infected, and/or did not close the wound properly to achieve good tissue alignment, and/or if you let the wound get dry and flaky, so a big dry scab forms (and then falls off prematurely), you are simply going to have a permanent mark there.
In other words, there is nothing you can really do "afterward" to heal a nasty scar; the key to minimizing scars lies in preventative measures.
Hope this helps,
Jack