Hi, I have started my 1st cycle, I have pinned my second shot last monday, today is my 3rd shot.

My right glute seems to still have a lump in it from my last pin, Just now have i started scratching around it and close to it, it has gone red due to me scratching it, Its really itchy but it isnt normal. Obviously i must go see a doctor.
If infected what will happen exactly?

All help will be appreciated Thanks.