I use my instincts when it comes to pus-filled small boils or abscesses. At first, when my dog got one of these, I took her straight to the vet because I was nervous that if I gently squeezed it out I might cause the infection to spread. When I got there, that was basically what the vet did. But they used veterinary antiseptic, (You could use Iodine perhaps?) -soaked a pad with this, rubbed it in, and squeezed until all the pus was out for sure. Then bathed it again with the antiseptic.
I was told though, that it was important to make sure the wound stayed open for a few days, and bathe the area three times a day, making sure that it wasn't filling up again, and being sure all the pus had come out. It was important to keep it open because if it healed over too quickly there could still be infected matter trapped inside. Bathing it with warm salt water is a good idea. Warm water will help to ease out any pus, and keep the wound open.
But I say "use your instincts" because only you know whether you think this needs a trip to the vet or not, and even possibly, a course of antibiotics, as it is just possible that an abscess, treated wrongly, can lead to complications or even septicemia.
To really be on the safe side, a quick trip to the vet (this will probably not cost very much at all) -may be the best plan.
Don't be upset if what's left after the pus is all out is an angry-looking dark red hole. If it's an abscess it probably will look a little like this before starting to heal nicely, leaving only a tiny scar in the end. (when fur grows back you probably won't even see it)
Keep an eye on your dog for any signs of lethargy, refusal to eat etc. If so -straight to the vet.
apply hot rag to bump and keep getting puss out with qtips use gloves and keep area clean should heal up in about three to four days