I am 22 weeks pregnant & my 11 month old was prescribed hydrocortisone valerate 0.2% for eczema, will getting this on me harm my unborn child?

No. Hydrocortisone is one of the weakest topical steroids (otherwise it wouldn't be used in infants), you wouldn't be exposed to much via transfer from you child, and very little of what gets on your skin gets into your bloodstream. Women who have asthma attacks while pregnant are treated with oral steroids, in doses millions of times higher than what you might absorb, and their babies come out fine.
No known harm. It is no problem for a pregnant woman to put Hydrocortisone cream on another child's eczema. The tiny tiny amounts of Hydrocortisone from contact with the cream and from contact with the other person's skin should not affect the woman's pregnancy or fetus.
General rule. As a rule, nothing you put on your skin surface will achieve a significant level in the blood.Since it doesn't, it cannot effect the fetus.The few exceptions include those prescription drugs that are given in patch form with special chemicals that allow it to enter the blood.