Thanks for writing in.
The patch of purple skin sounds like an organized haematoma
(collection of blood). This is not something serious that you need to worry about. Hot fomentation and locally applying diclofenac
ointment would probably help this become better. It is unlikely that the patch will resolve , but these measures will definitely help the pain.
I would not recommend a pain killer for this soreness as it would only work when given and is not a step in the right direction. Additionally, pain killers can cause damage to the kidneys when given over the long term.
Hope this helps