a) It is a tophus and is caused by gout attacks
b) there is a growth in the bone of the foot - but it is benign.
To find out what caused it, I visited the polyclinic for the first time in my life. I had to join 6 queues over 3 hours and only saw the doctor for 10 minutes. I now know why Singaporeans loved the time spent in queues - especially if they can take the time off from their work.
The polyclinic took an X-ray of my foot. The doctor studied the image and reported that is is most likely a tophus. I will be visiting a specialist in the hospital to see if they can remove the projection.