Unfortunately, a high resolution closeup photo would have been more helpful. From the history, however, it sounds as though you have what is known as a papular acne scar, which simply means that instead of having developed one of the far more common indented varieties of acne scars, the acne lesion that preceded it gave rise to a pimple-sized elevated scar. Flattening this scar, so that it does not stick out and becomes more flush with the surrounding normal skin may generally be achieved via one of three ways and occasionally through some combination of these approaches. The simplest approach is to inject it with an anti-inflammatory agent to shrink it, the way we would shrink a hypertrophic or keloid scar. A second approach is to numb the area with local anesthetic and flatten it by light electrodessication. And a third technique, once again under local anesthetic, is to simply "sculpt" the protruding portion off with a scalpel (horizontally, with no deep cutting and no need for stitches), the way one would aesthetically remove a simple mole (beauty mark). I suggest you consult with a board certified aesthetic physician so that the best approach can be chosen for your particular problem. Make sure to ask to see his/her before and after photos before proceeding.
The first I'd try is an injection with a steroid. If not happy after a couple months, I'd try Fraxel Laser or Infini. I wouldn't try shaving it with a scalpel or electrodesication. Both of these have the potential for making this worse.
I suggest seeing a cosmetic expert this can be treated with lasers, needling and injections. A formal consultation is needed. Best, Dr. Emer.
The most important factor is going to be avoiding any additional trauma to this lesion, including not only your hands but also sunlight. To specifically treat that scar you have a couple options, including some lasers and simpler treatment with a device called a hyfrecator, which creates electrical energy and is applied to the skin surface. Finally, scars such as this one can also but cut out, but i feel this would be the last option as it could result in scarring. You definitely want to seek out the help of a local dermatologist, who can help determine which treatment option is best for you.