Location of rhogam shot

So I got the shot at 20 weeks pregnant bc of spotting everything was ok well I’m gonna have to get it again around 35 weeks. 2 years ago I had it in my arm I can’t remember the pain from that but this time around I got it in my butt and it hurt so bad it stung and hurt to sit on for days. Does anyone know which one hurts the most or which one u have got and didn’t hurt as bad? The nurse said the butt hurts less bc there is more meat in it but like it’s just a awkward spot to get it.