A few months back I had to donate my sperm to a family who was unable to get a baby. Intitally the lady’s husband wad supposed to give his sperm however at the last moment the doctor came up that his sperm are not capable enough to do the work so I was contacted by him as thier efforts money and hopes were at stake. I donated mine without getting proper knowledge at this matter. Now they are happy and I am in sort of depression. What should I do now. I even dont know whether the eggs had been fertilised in the lab or lady’s womb. Can I be saved from hellfire?

You committed a forbidden act by masturbating to extract semen, and you must repent and seek forgiveness. And you, as a Muslim man, should not have made this donation, and you should not be embarrassed by their loss of money.
As for the woman’s vaccination, if the insemination took place and she became pregnant, then the boy is your son or daughter, and he is attached to you and the mother, not to the woman’s husband, and he inherits you and you inherit him.