Help with an I.M injection. Please Help?

I went a month ago to go get a depo provera shot. I asked the nurse to show me how to do it myself. My friend decided to get it too so i told her that i could give it to her. I payed very close attention to the nurse and have read everything about giving i.m injections. I am also in school for a health profession. I know I did it right but i still have a feeling maybe something could happen. I did the injection in the deltoid muscle. I used alcohol wipes to clean the area, inserted needle about half way (1 1/2'' ) like my nurse said, I aspirated to make sure i wasnt in a blood vessel, and gave the shot. I just want to know what could happen if i did it wrong. But im pretty sure I did it right. Thank you