Acne injection

I have acne problem (I can't claim that it is severe but it is affecting me to a certain extend), the blackhead scars left behind is rather annoying. Tried many types of facial products, wash and also this cream called 'diprosalic'. It feels rather itchy as well. A few days ago, my medical coursemate whose parents are both doctors told me about this injection that is used to treat acne and she also said that I will get a better complexion and the injection should be injected on the bum (gluteal region). What I am aware of so far is that, injections that are administered in the gluteal area are usually very strong and are usually given to relieve pain. I hope some people can shed some light as to whether such an injection is specially for acne or if it is some form of painkiller which has a side effect where it indirectly reduces acne.