Thanks for writing in.
It can be a hematoma(blood clot) under the skin. Be cautious.If you develop any of the following symptoms then you need to report to the ER immediately.
, persistent headache, vomiting, drowsiness
For the time being you can apply ice compresses to the affected area to prevent enhancement and spread of the redness
. In addition a mild analgesic
like paracetomol -ibuprfen combination willmake you comfortable.