It sounds like that was quite an accident, and I am glad that you did not hurt yourself more! It is pretty common when you have an abrasion like this one to have small bits of debris get embedded in the skin. The important thing when this happens, as you did, is to try to remove any loose debris and to take good care to clean the entire area. When this is doe, sometimes small bits remain, such as in your case.
As long as the cut is healing well and the debris is embedded on the outside, it should eventually just work its way out as the skin grows and turns over during the next few weeks. As long as there is no evidence of infection (such as redness, pain, or pus) then you can probably leave it alone.
Sometimes, the debris does actually get buried in the skin and doesn't work its way out. In these cases, occasionally it is helpful to see a doctor
to determine whether the foreign object should be removed or not.
If you have concerns, start by visiting your primary care doctor
who should be able to help you decide if you need to do something.