Sterile Abcess?

So after my last injection I have a lump about a quarter in size that will not go down at all. I'm starting to think that it is a sterile abcess, seeing as they usually go away after a couple days and this hasn't changed in 4 days now. Should I wait it out a bit longer and see if my body eventually absorbs it or should I head to the doctor? Also assuming it is just a sterile abcess, is that something I could pin and drain myself? Thanks in advance guys.