Jeremy S. Fenton, MD

It is unlikely this is related to the botox being injected too superficially.  Botox is injected as a liquid and the volume of that liquid is quickly absorbed by the body.  It is not like filler, it does not hang around for many months.  It is possible that you had some bruising from the trauma that is still residual.  I would recommend returning to your doctor to have them evaluate it.

When you have an itchy spot that you scratch for a long period, you can develop what is called lichen simplex chronicus, or a prurigo nodule.  These can create an itch/scratch cycle, because the nodules can be itchy themselves. The more you scratch, the worse it gets. Treatment for these includes steroid injections, steroid creams and tape, and freezing them with liquid nitrogen. However, the most important thing is that you stop scratching. 

Sometimes insect bites leave behind a retained insect part under the skin that causes a chronic allergic reaction. The only way to remove those is excise them. I would begin by treating the nodule and see if there is a remnant that continues to itch. 

Usually, the first treatment for keloid scars is to inject them with cortisone.  Surgical excision does carry a high rate of recurrence, so you often need to do something in addition to the excision such as aggressive injections, physical clasps, silicone gel sheets, or another preventative measure.

There are rare people who are resistant to Botox, and some patients develop antibodies to it after repeated treatments. In those patients, I recommend trying a different form of botulinum toxin such as Xeomin or Dysport.

The placement of the Botox is also important. If a physician places it too superficial, above the muscle, it may not have as much of an effect. 

After 55 units, most people should see at least diminished movement, depending on how those units were distributed. I would recommend

Scars such as the ones you have with variation in skin texture can be treated with certain lasers that perform "resurfacing."  These lasers stimulate collagen growth and can help normalize the texture and appearance.  Nothing will ever remove the scars completely, but these procedures can make significant improvement.  In somebody with your skin type I would recommend something safe for darker skin such as the Fraxel laser.  You need to be aware, however, that it will take several treatments to see a difference (3-4 at least) and that the amount of improvement can vary greatly between different people.