I did as you suggested & then at around 8 pm he started to cry out that he was in pain, that it felt like his finger was on fire. I checked it with my magnifying glass to see better. The area around the first joint was very red, the finger was a darker red, the skin shinny from the pressure. I noticed that the yellow area was closer to the surface, only a few layers below - but I also saw that the blue veins on the middle finger were raised up, like they do when they are stressed. They were thicker too... I made the guess that the pressure was impeding the blood flow in his finger.
This couldn't wait so I made a call, trusting my training, my experience & my instinct. I took a new sterile needle from the box I had in the closet. (I keep a box for my sister, who's diabetic, for when she visits.) I slipped it under the few layers of skin (that's how close to the surface it was.) Immediately the pus began to flow through and out the top. It was a yellowish and the consistency of custard. I removed the needle and it just flowed out, we used a fresh gauze pad to catch it. But soon needed a second and third. It just kept coming out, finally some pale pink blood came out, more pus mixed with clear liquid too. He was crying about the pain, but as the pressure stopped he said it wasn't throbbing or felt like fire, it just hurt bad.
The skin is bruised, (I didn't push on the area, just let it release the pressure, for a while it was just oozing on it's own. Mostly mixed fluid, but the swelling reduced considerably, the bright red around the first joint faded & the veins within a few minutes returned to normal as well. I know there is still more pus inside, the infection isn't completely removed. I gave him another ibuprofen, put some triple antibiotic ointment on it & gave him a fresh piece of gauze to put around it lightly to catch the fluid.
He was so happy that he gave me a hug & his big brother one for helping me. I'm still taking him into the doctor in the morning as he still needs to get some medicine & for the infection site to be evaluated also. But despite the bruising coloring, it looks so much better than before.
Thanks for all your help with this, I know that it was risky to drain this, but the risk not to do it was greater I felt. I hadn't thought of draining it till I saw how much pressure was building up & how close to the surface the infection had come. I didn't even try to puncture the secondary area that was a bit deeper. I'll let the doctor decide how to handle that part. I just needed to take care of the abscess that was building up inside. This turned out to be the correct move to help him.