Perfect, the ultrasound may tell us a lot about your problem. In the meanwhile try just to ice it (10 minute on 10 minutes off for not more than 3/4 time) if the pain is flaring up and gently stretch the extensor group of your forearm, ideally you want to work on the edge of discomfort, never push it to pain threshold.
http://www.toptenreviews.com/i/rev/s...e-stretch2.jpg (do what the guy is doing in the picture below, not the one on top)

plus if you have any relief period, don't work too hard immediatelly on your laptop/pc or piano activities, try to increase the workload bit by bit and carry on stretching gently the area.

I didn't ask you about any pain on neck as you were very clear saying that the problem is exquisitely in the forearm in that spot and when it gets bad then can radiate down to your fingers (which one exactly though?)