Subcutaneous hematoma

I am a diving instructor working in the Maldives, with Basic Professional DAN insurance. Almost 3 weeks ago I fell, whilst on a dive boat. A very large bruise appeared within a day or two. About 2 weeks later I felt a 1cm large, hard "bubble" under the skin. A nurse on the island thought it could be a thrombosis. Since then a smaller "bubble" has appeared beside the larger one. I have been diving throughout this period but am wondering what course of action should be taken, and if there is any cause for concern?

The condition you describe may be compatible with a large subcutaneous hematoma (blood under the skin). Normally these situations resolve spontaneously in some days / weeks and the subcutaneous blood is readsorbed. The treatment needed may depend of the magnitude of the injury, but frequently nothing more than time is necessary.
Without any clinically significant complication, pain or functional impairment, normally no special caution is required and a normal life and activity can be conducted.
However I would suggest an evaluation by a medical doctor to exclude the possibility of any other significant clinical complication.