I have a hard non painful lump about 2cm on my solar plexus which has doubled in size in the past 3 weeks could you please tell me some causes please?

See your PCP. For this one, you will need to see your pcp or a dermatologist. This could be one of many things, benign or malignant. However, it is likely to be a cyst if it is growing that fast and not painful. Have your pcp check it out. It is better to be safe on this.