What are the Small growths on top of hand?

It could be anything really. I would recommend speaking with your doctor or dermatologist if they concern you, especially if they are painful or begin to spread. They could be Pompholyx or Lichen Simplex Chronicus.

Pompholyx is a type of eczema that affects the hands and sometimes feet. The first symptoms you may notice would be tiny blisters deep in the skin of your palm, fingers, instep or toes. The blisters may cause itching or have a burning feeling. The cause is unknown, but some doctors believe it could be caused by abnormal sweating.

Lichen Simplex Chronicus is an itchy skin condition caused by thickened skin at the areas of skin injured by repeated scratching and rubbing. It begins by your skin itching. The itching then leads to scratching or rubbing, which causes the thickening of the skin. The thickened skin is also itchy, which causes more scratching and even more skin thickening. This cycle will continue unless treated.