There are many possibilities to be considered here; you could be having a skin diseases which could be caused by any germs or petechiae
due to subdermal hematoma
(its some kind of blood clot beneath the skin) as a result of the nails. But I do not think it is an allergy
. From your description, i will vote for the 2nd option. In that case, you need not worry as I do not think it has any fatal outcome.
Where as in the mean time you can pay a visit to the orthopedics for review. What is seen and examined is better than words
hope this helps