What are these unusual bumps on my hand?

That would be a Dermatlogy question look up warts too. People get them on their hands.

The medical answer could be Du Puytren's Contracture.  (Pronounced Dew Pwee

Tron)    it is  a condition in which  the tendons of the finger  thicken and get caught in the sheaths of  tendons. Hard lumps in the palm follow. The  condition can be inherited. It is common in men over 40. There is a tendency for it to be seen in persons of Viking descent  and also in people with cirrhosis of the liver If the  finger will not straighten  surgery of the hand should  solve the condition.It may not  remove the lumps from the palm.

Might be hyperkeratosis, which is really just a tendency to build up calluses. Those are building up on areas in contact with each other when your hand is in a closed position, like holding a game controller or stylus.

Can a person get plantar's warts on their hands? Because that's what it looks like to me.

you don't have cancer

Cancer or kidney disease? No. No link there.  Go see a dermatologist for a real diagnosis

Some kind of ingrown warts?