I would recommend that you visit your primary care doctor
. I can't confirm this diagnosis over the internet, but based on your description of what happened, it sounds like the most likely cause of these white spots is something called post inflammatory hypo pigmentation. This is a normal process when the skin is healing from trauma (such as from a cut or scratch); basically as the new skin tissue regenerates, there is a tendency for it to be more lightly colored than the surrounding undamaged skin.
Most of the time, post inflammatory hypo pigmentation doesn't require any specific treatment, and the color tends to normalize slowly over time, often however this will take weeks to months. Some people will try a topical steroid cream to speed up the process, but the evidence that this is actually helpful is pretty thin.
Again, I would recommend that you visit your primary care doctor to have them take a look at these spots. This is important because they can confirm whether or not this is indeed post inflammatory hypopigmentation, or whether it is another condition (such as eczema
or a fungal infection of the skin) that might require a specific medication treatment in order to clear up. Call and make an appointment today.