Welcome to HCM,
It seems that due to nature of your job as a machinist you got this problem.
There might be allergy
due to handling metal chips, oils etc.
Use hand gloves while on work.
After work wash your hands with plane clean water and apply some moisturizing lotion.
At present it seems that there is some infection due to severe itching
Go for one antibiotic after consulting your doctor.
Take antihistamine like Cetrizine
Apply local antibiotic
Ok and bye.