Rhogam after Chemical Pregnancy

I had a chemical pregnancy recently, and went to see my OB/GYN and he said he figured I was around 4 1/2 weeks when the pregnancy terminated itself. He stated that I had to have blood work to check my blood type, and if I was Rh- then I would have to have the rhogam injection. When my blood work came back, the labs showed that I am Rh-. He didn’t seem like it should be rushed or anything, he never stated a time frame, he just said that I would have to get the shot. So since then, and after researching, I see you have to have it within 72 hours. It’s now past 72 hours. Will this affect future pregnancies and does anyone have any similar experiences?